Which weekends in July and August is it least likely to rain?
Dear Tom,
I am in charge of planning an annual summer party and it has rained the last few
summers on the weekend chosen. Historically, which weekends in July and August is it
least likely to rain?
Bob Haza, Oak Brook, Ill.
Dear Bob,
When it comes to avoiding a rainy weekend, it doesn't matter which dates in July and
August you select. The chance of rain is the same on any given day in those months: 31
or 32 percent. That's the result of a computer scan of 137 years of Chicago's daily
rainfall records. You can attribute your rainouts in the last few years to bad luck rather
than to poor planning. But consider this: Thunderstorms account for most of Chicago's
mid- and late-summer rainfall, and August thunderstorms tend to be of shorter
duration. That suggests an August outing is slightly preferable. The tradeoff is that
August storms, on average, produce more intense (but more brief) rain.