Another heatwave is set to impact the state mid-week through this weekend, bringing several days of hot temperatures and high humidity to many areas.

A developing ridge across the Central US is expected to expand and strengthen, which will lead to very hot temperatures across a large portions of the U.S. A piece of this heat dome is expected to affect a good portion of the state the next several days. Things will kick off today with temps in the 90’s across portions of Southwest Illinois. These hot temps, along with high moisture levels and high heat index values, will spread across much of the state by Wednesday and Thursday, and last through the weekend.

Several consecutive days with high temps in the 90’s is likely across much of Central and Southern Illinois, with some areas in Southwestern Illinois potentially seeing a few days around 100 degrees. The St. Louis metro area will see the hottest temps, with several consecutive days in the lower 100’s likely. Further north across portions of Northern Illinois things will likely be tempered, with daily chances of thunderstorms, but warm and humid conditions can still be expected. Overnight low temps will likely remain well into the 70’s during this period, with urban locations, such as the St. Louis metro, staying in the 80’s overnight. In addition to the hot temperatures, high moisture levels are expected, which will lead to high heat index values for the period. Heat index values will likely be in the 100-110 range for much of Central and Southern Illinois during the period.

The combination of the high temps, high moisture levels and high heat indices for a prolonged time will lead to oppressive conditions for many areas. Outdoor activities should be limited during this time, and those with health issues should be watched. Heat stress and exhaustion will also be of concern.

It should be noted that there will be daily chances for thunderstorms, first farther north early in the week, eventually extending south as we head into the weekend. This activity and associated cloud debris could help temper the heat for some areas at times.