What a Difference a Summer Solstice Makes
May 24, 2017 01:53PM
● By Rick DiMaio
On June 20, at 11:24 p.m., Chicagoans can perform the annual ritual of saying hello to the sun on the first day of summer. The word solstice is from the Latin solstitium, from sol (sun) and stitium (to stop), reflecting the fact that the sun appears to stop at this time and again at the winter solstice.
With the anticipation of summer weather comes the inevitable planning of how to make this summer different and better than any summer, ever. There’s nothing like the anticipation of flipping through the calendar, staring at the coming summer and dreaming of warm days and all the things we’ll do to enjoy them. Whether it’s a short weekend jaunt to Galena, a weeklong trip to Door County, the two-week drive to the Grand Tetons or simply a staycation, one question permeates all summer planning—what will the weather be like?
Summer’s weather is our ultimate best friend or worst enemy. Temperatures in June average 75 on the 1st to 84 by the 30th. Overnight lows rarely drop below 60 and we typically get three to four inches of rainfall. July can get hot, with afternoon highs averaging close to 84 to 85 degrees most of the month with similar rainfall in June. August is our wettest month, with rainfall averaging close to five inches and afternoon temperatures routinely in the lower 80s. By the end of the month, overnight lows can drop into the lower 50s as the vernal equinox approaches.
However, recent questions regarding our Earth’s warming and the increasing variability of our seasons make a long range summer prediction slightly more challenging. By May, the Chicagoland area had already experienced 14 days above 70 degrees (twice the norm), two days above 80 degrees and nearly six inches more rain than last year. Oddly enough, we had less than one inch of snow in January and February combined. To make climate scientists rub their eyes even more, we had two days of 70 degrees in February, along with a tornado outbreak on the 28th, while we had only one day of 70 in March, along with eight to 16 inches of lake-effect snow.
Although the first half of May turned cooler than normal, many indicators show we are headed for a warmer (although not extremely hot) and wetter than normal summer. Although long-term rainfall is difficult to predict in summer, the effect of extremely wet soils from the spring rains and evapo-transpiration from crops into the atmosphere should generate more afternoon shower activity around the area. Keep that in mind when headed to a ballgame.
To sum it up, this summer, large scale warmth from very warm ocean waters globally will allow summer to become slightly warmer without much help from shorter term weather patterns. It’s hard to bet against a cooler than normal summer when the oceans continue to remain warm.
So here are the numbers: the normal number of 90s is 18, we should see one in May, four in June, eight in July and 12 in August, and possibly three or four in September. Rainfall will be highest in June and early July, with six to eight inches likely, leading to a late-season hot and humid two-to-three-week period in late July and early to mid-August.
While these numbers can easily go up and down, current short-term and long-term trends are pointing toward the second half of the summer acting more summerlike than the first half. For vacation procrastinators, that might work out well. For our 9-or-10-year-old household members, for which summers can go on forever, tell them that the meteorologist says, “Just make sure you clean up your room when your mom asks, so you can be the first one outside to build that fort or catch the elusive firefly.”
Rick DiMaio is a professional meteorologist and climate scientist heard on The Mike Nowak Show on 1590 WCGO and at MikeNowak.net, and has been seen lately on Fox 32 Chicago TV.