Peoria, ILL. (WMBD) — Summer-like heat has built into Central Illinois resulting in near record high temperatures in the upper 80s and lower 90s. Temperatures are expected to remain well above average through the end of the week before a cooler weather pattern moves in for the weekend and next week.

Temperatures are expected to top out in the lower 90s on Wednesday and Thursday with heat index values between 95° and 100° both days. Peoria is forecasts to hit a high of 91° on Wednesday which would tie the previous record set back in 2011. Thursday’s record high for the Peoria area is 92° set back in 1956, and while the current forecast (90°) has our temperatures falling short, it is certainly within reach. If we do manage to hit a high of 90° or higher on Wednesday, it would be the earliest 90° day since May 10th, 2011. You can see a few more first 90° stats below. The 30 year mean first 90° day is June 5th.

YearDate of First 90° Day
2011May 10th
2012May 19th
2013June 12th
2014May 12th
2015June 7th
2016May 30th
2017June 4th
2018May 14th
2019June 29th
2020June 2nd
2021June 10th

In addition to setting record high temperatures, parts of Central Illinois could set record warm-lows in the coming nights. In fact Peoria tied it’s record warm-low of 69° Tuesday morning and could break Wednesday’s record warm-low of 70° tonight with a projected low of 71°.

What’s causing the heat?

A powerful ridge of high pressure has built in across the Midwest resulting in well above average temperatures across the state. With high pressure overhead, air from aloft is brought down to the surface, compressing, drying and warming as it descends. This usually results in warmer and sunnier days with high pressure in place.

The next piece of the puzzle was strong warm advection in association with a deep low-pressure center across the Central and Northern Plains. You remember those strong southerly winds we experienced on Sunday and Monday? Those winds ushered in a much warmer and muggier airmass, add in the sprawling ridge of high pressure mentioned above and now you have conditions right for near record setting heat.

Any connection to climate change?

It’s been well documented the Spring temperatures have warmed since the start of the 20th century (Figure 1) and that warmth is largely attributed to climate change. Interestingly enough, while Spring temperatures have warmed there’s been no discernible trend in our Summer temperatures (Figure 2). In fact, the hottest summer temperatures occurred during the 1930s Dust Bowl, which isn’t surprising given that temperatures warm more when the air is dry rather than humid, and widespread drought would result in warmer temperatures. This trend is even more obvious when you look at the number of very hot days since 1900 (Figure 3) which actually shows a sharp decline since the 1930s.

The following charts are courtesy of the 2022 Illinois Climate Summary

It’s important to remember that there’s a difference between climate and weather. Climate represents long term trends over decades while weather is what’s happening now, tomorrow, and in the weeks ahead. So while temperatures have generally warmed over the past 120 years, individual heatwaves such as what we are experiencing now are not a direct result of climate change.