Sioux City, Iowa hit 106 degrees yesterday. This after getting an unprecedented snowfall earlier in the month. Temperatures rose 77 degrees in only 56 hours.
Chicago officially hit 91 degrees after being at 36 degrees the previous morning. That makes it the highest temperature swing ever recorded for May.
Many other 100+ degree temperatures were recorded. The highest was 108 in Broken Bow, Iowa.
The extreme temperatures are due to an extreme jet stream. There is a huge bow in the jet stream allowing cold air to flood in from Canada and behind that bow is a giant surge of warm air that stretches north to Canada. The jet stream does look like this from time to time during the summer and it’s usually how the most violent summer storms come to be. A jet stream configuration like this happening in May is extremely unusual.