Forecast Models Predict Arctic Blast for Illinois in August

How much do you trust computer models? That's the crucial question when it comes to what weather to expect in Illinois in August. A consensus of forecast models are in agreement that cooler air will permeate Illinois in August, for forecasters are not buying it - yet.

In the last few days, the Direct Weather YouTube Channel noticed something interesting involving what computer models were showing over Illinois and other Midwestern states during August. He shared what the GFS extended computer models were showing which is a combined outlook for August averaging out what dozens of simulations are showing. This is what the temperatures look like over Illinois right now which is why we've had a break from the heatwave of the past several weeks.

When you move it forward a few more days, you see that temperatures warm up around August 11, 2025, but that won't last long.

Looking further into August, another blast of cooler air once again dips temperatures below the Illinois' normal during this time of year.

When you look at the last week of August, the cooler trend looks even more pronounced.

If you peek ahead into September, the cooler than normal trend continues for Illinois.

You can see his breakdown of this odd August temperature trend for Illinois at around the 13 minute mark in his video. He does give caution to putting too much weight on models that are this far down the road.

What do National Weather Service forecasters say about August for Illinois?

The National Weather Service in Chicago is not on board with the idea that Fall might be arriving early yet. NOAA's Climate Prediction Center predicts the opposite of what these models show as they believe the state will see ABOVE normal temperatures at least for the next few weeks.

I am not a meteorologist so my take on these predictions is unimportant. However, I am a computer tech when I'm not scaring people on the radio and I can tell you that computer models depend on data and variables. All it takes is one tiny variable to change and that can completely alter the results of month-long temperature outlooks like this. It might really cool down and stay that way for most of August, but time will tell the tale if it's meteorologists or computer models that are right about what Illinois can expect the rest of August to be.