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C-U Monthly Weather Review: May 2023

a picture looking up at the blue sky with white streaky clouds and the sun behind them.
Andrew Pritchard

For the second year in a row, we’ve seen spring rains disappear from central Illinois. Aside from a round of thunderstorms during the first weekend in May, we’ve seen persistent sunny and dry conditions across the region. For a while that’s been great — farmers had a successful planting season and outdoor activities are off to a fast start this season— Now however, the dryness is starting to mount and we’re again seeing some drought begin to emerge across the region. Let’s talk about the month that was May 2023 in Champaign-Urbana.

May came in warmer than average overall, which was expected and mentioned in my last monthly weather review. The mean temperature for the month was 64.8 deg F, 1.6 deg warmer than average. We saw a seasonally appropriate gradual increase in temperatures beginning with highs in the 50s and 60s early in the month, to our first time hitting 90 degrees on the last day of May. A final way of looking at May temperatures — out of the 31 days in May, 21 days had temperatures warmer than the average for that date.

The precipitation story is rather simple. We saw thunderstorms and heavy rains on May 7th and 8th that produced vivid lightning and delivered almost two inches of rain to the area. Unfortunately, that was about it for the month. Light showers dropped a few hundredths of an inch mid-month, but it’s been a dry three weeks otherwise, during a time of year that should be quite stormy. Total precipitation in Champaign-Urbana for May 2023 was 1.98”, well below the average of 4.78”.

A brown brick building with a clock tower in the center, sits on a corner surrounded by green leafy trees. The sky is blue with a few whispy clouds behind.
Andrew Pritchard

What caused all of this? To put it simply, the jet stream (that river of air flowing above our heads where commercial airliners fly) has been blocked up and shut down over the Central U.S. Without those swiftly flowing jet stream winds, there are no storm systems, there is no variety to the weather. It’s just sunny, quiet, and mild. Instead, jet stream winds have focused rain and storms on parts of the High Plains across Texas, Kansas, Oklahoma, and Colorado where they’ve badly needed the moisture after three straight years of La Nina induced drought in those states.

So, where’s our rain? It’s coming! If you skim back through the April 2023 review, my forecast for May mentioned the long-term outlook showing a pivot toward stormier conditions in the Midwest, but that this would take some time. Over the next week or two we’ll finally begin to see this blocked jet stream pattern break down. That should allow for the jet stream to reorganize and begin sending storm systems back through the Midwest. Now, the summer months are not typically a time for fast, organized jet stream flow as it begins to lift into Canada, but this should open us up to what would be a more typical June weather pattern in Central Illinois with periods of showers and thunderstorms returning to the region every few days. Right now, this transition looks like it will happen around June 10th. Will we suddenly shift from a sunny, hot, and dry pattern into one that offers frequent storms and heavy rains? That much we’ll have to watch together as we head through the next couple of weeks. I do think that by mid-month we are at least working showers and storms back into the forecast.

Temperatures are likely to be around average, maybe a little warmer for the month of June in Champaign-Urbana. We’re certainly off to a hot start, with the first weekend sending temperatures soaring into the middle 90s. We’ll see some relief in the form of cooler temperatures by the end of the first week of June, and I think that’s a general pattern that follows through the entire month. Periods of hot temperatures, high humidity, and general storminess, followed by stretches of sunny, dry, and comfortable weather.

Andrew operates Chambana Weather, where he publishes daily weather information for Champaign-Urbana and surrounding communities. He also serves as Senior Meteorologist with Nutrien Ag Solutions at Research Park, focused on domestic and international weather and its impact on agriculture.

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