Widely dispersed emerging thunderstorms Wednesday dumped 0.29 inches of rain at O’Hare, Chicago’s official weather site. It was enough to push the month’s rainfall total above the half-inch mark, but the 0.71-inch will still be one of the driest Mays ever recorded for the city.
How bad is this dry spell?
Right now, the city is experiencing a flash drought, which is still a drought, just one that occurs when conditions deteriorate rapidly, in a matter of weeks rather than months, explained Trent Ford, Illinois state climatologist.
After a relatively normal early spring in terms of rainfall, the Chicago region completely dried out in May, almost 4 inches below normal, which, ironically, made it a pretty nice month, Ford said.
“Drought weather is usually very, very nice in the spring,” he said, with sunny skies and low humidity. But those same conditions also pull water out of the ground, especially with the hotter temperatures the city has seen in recent days, Ford added.
The ground is now dry 8 to 10 inches down, he said, and the turf, given the grass’s shallow roots, is the first to show the effects, turning from bright green to yellow, green, gray and crisp. (The good news is that people should avoid mowing the lawn.)
Lake Michigan is not at risk, but smaller streams and ponds are drying up, and drought-sensitive shrubs and plants, as well as young trees, are likely feeling stress as well, Ford said. Thanks to irrigation systems and drought-resistant seed varieties, agricultural crops, particularly staples like corn and beans, have so far not been affected.
That could change if the region doesn’t get soaked soon.
The National Oceanic and Atmospheric Administration’s Climate Prediction Center has forecast above-normal rainfall for Chicago in July and August, but that forecast is highly dependent on past performance during El Nino years, Ford said.
“If we’re trending toward that pattern, that’s great,” he said, but there’s a great deal of uncertainty in the prediction.
The current drought actually shows how difficult it is to project how Mother Nature will behave.
Forecasters accurately forecast a dry spell in May, but “I’m not sure we expected it to persist,” Ford said.
The lack of rain is due to a high pressure system that is essentially parked over the Midwest. “We expect the high pressure to move to the east, but it has persisted for almost three weeks,” he said.
In effect, the system has prevented humid air from the Gulf of Mexico from reaching Chicago. It’s also pushing the air down, which is the opposite of the push needed to make it rain, Ford said.
He encouraged people to report what they’re seeing locally, even if everything looks good, through an online drought observation tool, which gives climatologists a better understanding of what’s really happening on the ground.
The next two weeks will paint a better picture of the importance of the drought, Ford said.
“Right now, it’s not great. But I’m not alarmed yet,” he said. “We’ll have to see if we get a break in June.”
Contact Patty Wetli: @pattywetli | (773) 509-5623 | [email protected]