WGN Weather Center Blog

To no one’s surprise, July ended up to be warmer and drier than normal in Chicago. Though severe thunderstorms brought some much-needed rain to scattered localities, the overall drought worsened across the area during the month. The hot summer continued with seven 90° days at O’Hare and 10 at Midway during the month, highlighted by the region’s first 100º day in six years on July 24 when O’Hare soared to 102º and Midway to 104º.
August’s opening days promise a continuation of this hot, dry pattern with four consecutive days in the 90s expected through Thursday, along with little chance of significant rainfall.
Rain is falling in other parts of the nation. Up to 4 inches of rain flooded the streets of Sylvania in east-central Georgia Sunday, while vehicles were stranded in up to 3 feet of water in east-central North Carolina near Greenville after heavy thunderstorms passed through the area.

Posted by wgnweather at 8:08 PM | Permalink

Posted by wgnweather at 8:07 PM | Permalink

Posted by wgnweather at 8:03 PM | Permalink

Posted by wgnweather at 8:01 PM | Permalink

After a short respite, heat and humidity will return to Chicago this week for what appears to be a lengthy stay.
Afternoon maximum temperatures should climb into the 90s today—an event that promises to repeat itself each afternoon through Thursday.
For the most part, prospects for precipitation remain bleak, though an isolated thunderstorm could develop on a hot and increasingly humid Monday afternoon. The week’s best chances for rain will occur Thursday night as a cold frontal passage brings the city another refreshing break after a week of hot weather.
With the recent demise of Tropical Storm Franklin, the Atlantic Basin is currently tropical cyclone-free, but things could change quickly in the next day or two if a strengthening tropical wave approaching the Windward Islands becomes the eighth storm of the season: Harvey.

Posted by wgnweather at 7:53 PM | Permalink

Posted by wgnweather at 7:49 PM | Permalink

Posted by wgnweather at 7:46 PM | Permalink

Posted by wgnweather at 7:40 PM | Permalink

More heat’s on the way. Temperatures and humidities will remain comfortable Saturday, thanks in part to easterly winds off Lake Michigan. But, with the ninth weekend of meteorological summer 2005 underway, the area is bracing for a new round of hot weather. A huge, rain-free dome of hot air continues to develop across the nation’s mid-section. Readings soared above 100° in parts of the Plains Friday, and this hot air is to begin building eastward.
Though daytime highs here won’t be as extreme as last Sunday’s 102°, surging humidities promise to make the five days of 90s predicted Sunday through Thursday rather uncomfortable: Gulf Coast-level dew points near 70° on the hottest of those days may send heat indexes near 100°.
Six of eight summer weekends this season have posted temperature surpluses, averaging nearly 5 degrees above normal. It’s likely this weekend will become the seventh to finish above normal.

Posted by wgnweather at 11:34 PM | Permalink

Posted by wgnweather at 11:32 PM | Permalink

Posted by wgnweather at 11:31 PM | Permalink

Posted by wgnweather at 11:29 PM | Permalink

Chicagoans are treated to another day of comfortable temperatures and humidities Friday. The day’s strengthening NE winds off Lake Michigan—and of Canadian origin—limit highs in all but far west and south suburban areas to levels below the normal high of 84°.
For a second consecutive day Thursday, the afternoon high (79°) here failed to reach 80°. In a summer with temperature stats which have so consistently been on the high end of the spectrum, it’s little surprise this summer’s tally of just 11 days in the 70s (26 is the long-term average since 1871 by this date) is so rare. Only two of the past 135 years—1944 and 1949, with 10 and nine days of 70s respectively—have produced fewer “cool” daytime summer highs.
The chill was more evident in the upper Midwest early Thursday. There, morning lows dipped to 38° at Tower and 44° at Embarrass—both in Minnesota.

Posted by wgnweather at 11:32 PM | Permalink

Posted by wgnweather at 11:30 PM | Permalink

Posted by wgnweather at 11:29 PM | Permalink

Posted by wgnweather at 11:27 PM | Permalink

It was the East Coast rather than sections of the Midwest which baked in record triple-digit heat Wednesday. For the first time in weeks, temperatures backed away from the 90s and 100s across the nation’s heartland. The dramatic pullback included Chicago’s September-level 74° high at O’Hare—the city’s lowest daytime high in nearly six weeks. It hasn’t been cooler here since 71° on June 18. The retreat was especially noticeable in a summer over which daily highs have finished, by a margin of nearly 6 to 1, above rather than below normal. The nearly two-month period since June 1 now ranks 6th warmest of all comparable periods on record here since 1871. It is also the 7th driest June 1-July 28 period in that 135 year span—and that’s with Tuesday’s beneficial rains included.
The heat was intense to the east Wednesday. Record highs included 100° at New York’s La Guardia Airport, 101° at Newark, N.J., and 102° at Raleigh, N.C.

Posted by wgnweather at 11:06 PM | Permalink

Posted by wgnweather at 11:05 PM | Permalink

Posted by wgnweather at 10:54 PM | Permalink

Posted by wgnweather at 10:52 PM | Permalink

Had they happened just weeks ago, Tuesday evening’s drenching downpours would have constituted a “million-dollar rain” for northern and central Illinois corn farmers, who have watched four months of drought ravage the region’s corn plants. But, while the rains are too late for the area’s decimated 2005 corn crop, WGN Radio agriculture broadcaster Max Armstrong says soybeans may be another story. Soybean pods are reaching a critical stage in the days and weeks immediately ahead, says Armstrong—setting and filling out. Rain is essential for success in this process and will play a major role in determining the ultimate soybean yield at harvest time. Precisely how much Tuesday’s rains have helped will become clearer in the weeks ahead.
Unusual by summer standards because of its uniform distribution, the rain was the heaviest to fall in the city in two months (since 1.26” on May 19).

Posted by wgnweather at 10:59 PM | Permalink

Posted by wgnweather at 10:56 PM | Permalink

Posted by wgnweather at 10:54 PM | Permalink

Posted by wgnweather at 10:50 PM | Permalink

SEVERE THUNDERSTORM STRIKES ARLINGTON HEIGHTS MONDAY EVENING

Monday evening a severe thunderstorm packing winds to about 60 m.p.h., torrential rainfall and lots of thunder and lightning raced through the northeast portion of Arlington Heights. Rainfall totaled .92" which fell in blinding torrents in a span of just 15 minutes. This morning the streets are littered with twigs, leaves and small branches which succumbed to the storm's strong, gusty winds. The lightning during the storm was intense with many cloud to ground strikes. One clap of thunder was so loud that our whole house shook. I was sure that it had hit close by and this morning I discovered what had happened. A large tree in nearby Wildwood Park had been struck with a large limb split open and nearly severed from the tree.

A tree in Wildwood Park struck by lightning in Monday evening's storm.

Burn marks where lightning bolt hit

Another close-up view of burn marks

Posted by wgnweather at 12:43 PM | Permalink

Summer’s never been hotter at Midway Airport. The 77.2° average temperature at the site since June 1 is the hottest on the books since observations began there in 1928. The reading is 4.7 degrees above the 77-year average and more than 6 degrees warmer than last year.
Some active clusters of thunderstorms combined with winds off the lake spared Chicago the brutal heat through which downstate residents suffered Monday. Moisture levels there were more typical of a tropical rain forest than the Midwest. In combination with triple-digit air temperatures, heat indexes soared into dangerous territory, reaching 110° or more in locations as close as Bloomington (111°) and Pontiac (116°).
Chicago’s relatively restrained 89° high at O’Hare was offset by the year’s muggiest dew points. At 3 a.m. Monday, O’Hare’s dew point hit 76°, while Northerly Island on the city’s lakefront soared to 79° around 9 p.m. Monday.

Posted by wgnweather at 11:08 PM | Permalink

Posted by wgnweather at 11:05 PM | Permalink

Posted by wgnweather at 11:00 PM | Permalink

Posted by wgnweather at 10:58 PM | Permalink

From shortly after noon until early evening Sunday, temperatures hovered at or over 100° across the Chicago metro area. Strong westerly winds drove a warm tongue of low-level heat from the mid-Mississippi Valley across northern Illinois, but these strong winds did alleviate the potentially deadly effects of a higher heat index by mixing drier air aloft to the surface.
As a result, dew points dropped from the mid 70s into the lower 60s—in effect cutting the potential 115°-120° heat index values back into the 103°-107° degree range. For example, veteran weather observer Frank Wachowski reported at Midway Airport that the dew point at 8 a.m. was 75°—the highest of the summer—but as the strong winds mixed in drier air from aloft, the dew point slowly but steadily fell, reaching 63° by mid-afternoon. This diluting of moisture near the ground significantly reduced reported heat index values by approximately 15 degrees.

Posted by wgnweather at 9:15 PM | Permalink

Posted by wgnweather at 9:13 PM | Permalink

Posted by wgnweather at 9:11 PM | Permalink

Posted by wgnweather at 9:09 PM | Permalink

At 2:52 p.m. this afternoon the thermometer at O'Hare Airport reached 102º making today the hottest day in the city since the mercury peaked at 104º on July 13, 1995 during Chicago's tragic killer heat wave. That same day Midway Airport broiled at 106º. Midway observer Frank Wachowski reports a high so far today of 104º recorded at 2:40 p.m. equalling the 104º high reached there on July 30, 1999.

Steve Kahn WGN-TV/Chicago Tribune Meteorologist

Posted by wgnweather at 3:15 PM | Permalink

IT'S OFFICIAL-- FIRST CHICAGO 100S IN SIX YEARS--TEMPS STILL CLIMBING

At 1:08 p.m. this afternoon the city's official thermometer at O'Hare Airport reached 100º. This is Chicago's 61st official 100º day on the books and the city's first since the high of 101º reached on July 30, 1999.

Midway Airport observer Frank Wachowski reported a high of 103º
so far this afternoon that was recorded at 1:45 p.m. CDT. With brisk west southwest winds, there is also no lake cooling with Northerly Island also reaching a high temperature of 100º. With several hours of peak heating ahead, it is likely that readings will surge even higher.

The record high temperature for today is 105º recorded in 1934 and is also Chicago's all-time official record high.

Posted by wgnweather at 1:42 PM | Permalink

Seventy one years ago today, on July 24, 1934, Chicago established its all-time official high temperature of 105º, and today’s triple-digit maximums should not be far behind. A hot air dome that sent temperatures soaring to as high as 110º in eastern South Dakota Saturday will surge into the Midwest today, bringing Chicago its first 100º weather in six years.
A long-lasting line of thunderstorms called a derecho that packed winds as high as 85 m.p.h. formed just north of the area of heat and humidity Saturday, sweeping out a swath of wind damage from northeast South Dakota to southeast Wisconsin. The storms dissipated just before reaching northeast Illinois, depriving this region of much needed rain, but sparing the area from power outages just before the intense heat moves in.
Hot weather will last into Monday before northeast winds bring much more comfortable conditions for the remainder of the week.

Posted by wgnweather at 9:31 PM | Permalink

Posted by wgnweather at 9:30 PM | Permalink

Posted by wgnweather at 9:28 PM | Permalink

Posted by wgnweather at 9:25 PM | Permalink

Chicago hasn’t recorded a triple-digit high since July of 1999. That changes Sunday as SW winds whisk intensely hot air into the area, a development which may well produce only the 61st official high at or above 100° here since records began in 1871. (Note: The heat-enhancing “urban heat island” effect has led to a greater number of 100s at the Midway Airport observation site, which has logged 83 days of triple-digit readings since 1928). Advisories for heat have been posted by the National Weather Service across 18 states this weekend from South Carolina west to Texas.
The effects of hot weather led to the hospitalization of 18 people in Paducah, Mayfield and Fulton, Ky. Heat indexes there ranged from 105°-115°. Drought conditions continue to make news. Rainfall at the Quad Cities so far this year is the driest since records began—drier than the Dust Bowl years of the 1930s. And Duluth, Minn., has experienced the driest July in the past 57 years.

Posted by wgnweather at 12:09 AM | Permalink

Posted by wgnweather at 12:08 AM | Permalink

Posted by wgnweather at 12:06 AM | Permalink

Posted by wgnweather at 12:04 AM | Permalink

Downstate Illinois and Indiana are in the grip of one of the hottest air masses in years and there’s no relief in sight until the middle of next week. It’s the same intensely hot air mass expected to sweep into Chicago Sunday and Monday. Even as clusters of downpour-generating thunderstorms whacked Chicago’s northwest and southeast suburbs Thursday, afternoon heat indexes soared above 100° for a second day as close as Kankakee (102°) and Bloomington (112°). Dewpoints, a measure of atmospheric moisture—considered uncomfortable at 70°—surged to 80° downstate. The atmosphere rarely holds more moisture in the Midwest.
Thursday’s powerful storms drenched Lafayette, Indiana with 1.59” while 0.60” fell at Valparaiso. By contrast, South Bend received only 0.20”, underscoring the selective nature of summer rainfall.

Posted by wgnweather at 11:17 PM | Permalink

Posted by wgnweather at 11:15 PM | Permalink

Posted by wgnweather at 11:10 PM | Permalink

Posted by wgnweather at 11:08 PM | Permalink

WHAT IS A GUSTNADO?

A possible gustnado caused considerable damage in portions of Lake County Illinois early Wednesday afternoon near the town of Wildwood as a line of severe thunderstorms raced through the area. The gustnado typically forms along the leading edge of a thunderstorm outflow boundary called a gust front. Below is a feature from the Chicago Tribune weather page archives done several years ago explaining this unusual meteorological occurrence.

Posted by wgnweather at 4:43 PM | Permalink

Posted by wgnweather at 10:29 PM | Permalink

Wednesday’s thunderstorms unexpectedly held together after crossing the Mississippi and surged into Chicago with the most rain in nearly 5 weeks. The price to pay was scattered severe weather, including widespread tree damage and a gustnado (a mini tornado at the leading edge of a thunderstorm) in Lake county, Ill., and 69 m.p.h. winds at Coal City southwest of Joliet. The reward was 0.60 in. of rain at O’Hare, the heaviest rain there in two months. Statewide the drought has crippled the corn crop, with 55 percent in poor to very poor condition. Last year at this time, only 2 percent of the crop suffered.
Meanwhile, heat in the West continues to build into the Plains. 100°+ temperatures were common across Kansas and Nebraska, and reached as far east as Quincy, Ill. A weak cold front inches into the area Friday, delaying the onset of scorching heat here until Sunday and Monday. Significant heat relief finally settles in next Wednesday.

Posted by wgnweather at 10:25 PM | Permalink

Posted by wgnweather at 10:24 PM | Permalink

Posted by wgnweather at 10:22 PM | Permalink

Even with the passage of a cold front Monday and the shift to northwest winds that followed, both O’Hare and Midway managed to reach 90° or higher on Tuesday, the fourth consecutive day of 90°+. Once again, low dew points made the heat tolerable, this time due to a fresh change of air mass rather than drought-induced dry air of days past.
Cooler air in the 80s wedged south into Minnesota and Iowa with this cold front, but west of that especially hot air continues to build in the high Plains and Rockies. Las Vegas broke six high temperature records Tuesday, including 117° which tied their all-time high set July 24, 1942.
This heat continues its unstoppable march eastward in upcoming days, reaching Chicago on the weekend. The first relief from these torrid temperatures finally arrives next Tuesday, along with a chance for meaningful rain.

Posted by wgnweather at 10:00 PM | Permalink

Posted by wgnweather at 9:42 PM | Permalink

Posted by wgnweather at 9:36 PM | Permalink

Posted by wgnweather at 9:21 PM | Permalink

A weak cold front swept through Chicago during the lunch hour Monday, but once again, significant rain failed to materialize until the system was south and east of the city. O’Hare received no rain, while Midway collected only .08". Already the driest summer on record to date, a scant 0.2" of rain has fallen at O’Hare in the 7+ weeks since June 10. Meanwhile, heat statistics are adding up. O’Hare’s 91° and Midway’s 92° are the 13th and 19th days respectively of 90° days in Chicago this summer, more than the last two summers combined.
Monday’s cold front provides one day of relief from the ongoing heat. Another brief cold frontal passage is likely again on Thursday, with oppressive heat to follow over the weekend and into next week. Rain with frontal passage is likely on Thursday, but the computer models have not distinguished themselves and have consistently under forecast temperature and over forecast rain all summer.

Posted by wgnweather at 10:45 PM | Permalink

Posted by wgnweather at 10:44 PM | Permalink

Posted by wgnweather at 10:31 PM | Permalink

Posted by wgnweather at 10:00 AM | Permalink

O’Hare’s 97° on Sunday was the hottest day since 101° on July 31, 1999. Again, the heat was made more tolerable by low dew points. The heat should break on Monday with the passage of a cold front and a gradual shift to northwest winds—but the front is weak, and temperatures will remain above normal Tuesday.
Today, Chicago enters the warmest period of normal temperatures for the year, 10 days with an average a high of 84° and a low of 64°. After the brief heat relief, temperatures turn back up on Wednesday, climbing each day to follow and peaking around 100° next weekend.
Meanwhile, the extreme drought retains its grip on the area. Rain with Monday’s cold front will be scattered, and even the computer models are backing off on totals, predicting only a scant few hundredths of an inch. Thursday now looks like a better bet for rain as another weak cold front approaches from the northwest.

Posted by wgnweather at 10:21 PM | Permalink

Posted by wgnweather at 10:20 PM | Permalink

Posted by wgnweather at 10:18 PM | Permalink

Posted by wgnweather at 10:17 PM | Permalink

MCDONALD CREEK- BONE DRY

The drought of 2005 is taking its toll. Since May 1, I have measured only 1.5 inches of rain at my house, and more than half of that fell in just 30 minutes during one heavy thunderstorm on the 4th of July. Area soils are parched and cracked and unwatered area vegetation is severely stressed and in some cases dying.

Having lived in the northeast part of Arlington Heights for more than 35 years and frequently crossing and viewing nearby McDonald Creek, I have never ever seen it bone dry like I did today on my daily walk around Lake Arlington. After a torrential rain McDonald Creek can be a raging torrent, but usually it is a lazy, low flow creek. However, today for the first time in my memory, McDonald Creek is totally dry, another casualty of the increasingly severe Drought of 2005.

A view of McDonald Creek

McDonald Creek as seen from the west bridge leading to Lake Arlington

Posted by wgnweather at 11:34 AM | Permalink

Saturday’s 93° at O’Hare—the highest so far this July—brought the 2005 total of 90° days to 11, with 17 days at Midway. Fortunately, afternoon dew points dropped to the low 60s and upper 50s, making the heat more tolerable. Low and fluctuating dew points are often a characteristic of drought summers. Sunday should reach the mid 90s for all areas but the lakefront, while light southwest winds pump in enough low level moisture to keep dew points in the uncomfortable range.
After a muggy night, Monday starts out warm. Clouds move in from the west with the best chance of widespread rain in weeks. The caveat is drought; it’s not unusual to see a good chance of rain in computer models dissipate before reaching a drought area.
Meanwhile, major hurricane Emily crosses the Yucatan late Sunday into Monday with a steady northwest track into the Mexican mainland. There’s little chance that any hurricane moisture eventually reaches Chicago.

Posted by wgnweather at 9:18 PM | Permalink

Posted by wgnweather at 9:10 PM | Permalink

Posted by wgnweather at 8:12 PM | Permalink

Posted by wgnweather at 7:34 PM | Permalink

Across drought-stricken northeast Illinois, Friday’s “hit and miss” thunderstorms were mostly a miss. The day’s muggy air managed to generate only a single thunderstorm of consequence, but what an event it was. An early afternoon deluge put down 2 3/4 inches of water just to the northeast of Kankakee. In the immediate Chicago area, however, showers were so brief and light that they went practically unnoticed.
The world’s heaviest one-month rain total, an incredible 366.14 inches, happens to be a July event. That rain, ten times Chicago’s average annual total, all came down in July, 1861, at Cherrapunji, India, and it’s a record that survives to the present.
At the U.S. South Pole Station in Antarctica, temperatures in July of 1997 averaged 86.8ºF below zero, thereby establishing a new record for the world’s coldest month.

Posted by wgnweather at 12:29 AM | Permalink

Posted by wgnweather at 12:25 AM | Permalink

Posted by wgnweather at 12:21 AM | Permalink

Posted by wgnweather at 12:12 AM | Permalink

That’s the word from Max Mayfield, Director of the National Hurricane Center in Miami. And now that the 2005 hurricane season has gotten off to a record fast start, his admonition is especially relevant.
Dr. Mayfield is referring to the tendency of the public to focus its attention on the narrow line defining the predicted movement of a hurricane core rather than the “cone” of possible movement of the storm system.
Mayfield also emphasizes that tropical storms and hurricanes are not discrete points on a map. Rather, they are sprawling weather systems that produce dangerous and damaging weather conditions in a belt sometimes 300 miles on either side of the center path.
A hurricane’s arsenal of potentially deadly weapons includes high winds, coastal storm surge, isolated tornadoes and inland river and flash flooding.

Posted by wgnweather at 10:20 PM | Permalink

Posted by wgnweather at 10:18 PM | Permalink

Posted by wgnweather at 10:14 PM | Permalink

Posted by wgnweather at 10:11 PM | Permalink

Popularly, “the Dog Days of Summer” refer to the hottest and most humid portion of the summer season—the period extending from early July into mid August. It’s a time of relative inactivity and stagnation, and even the weather seems to slow down. That’s certainly the case right now.
Jet stream winds, important because they steer air masses and storm systems and, broadly speaking, keep weather systems moving along, have shifted north into Canada. Computer models say that’s not likely to change significantly in upcoming days.
Locally, the atmosphere has become lethargic. The remnant remains of Hurricane Dennis have stalled over the Ohio Valley and are gradually fading away. Lingering showers, too, are dissipating. Hazy, warm and humid air now in residence will stick around, and grow even warmer this week as the hot July sun works on it.

Posted by wgnweather at 10:16 PM | Permalink