The hottest day of the week is expected today across south central Iowa. An excessive heat warning was expanded west, and now includes Marion and Warren Counties. Heat index values will likely approach 110 degrees in the afternoon and early evening hours. Outdoor activities will be difficult and become more dangerous with prolonged exposure, and heat exhaustion is a concern for those not taking proper precautions.

Following the heat, scattered thunderstorms will form over the state tonight, many of which could be severe. Strong winds, large hail, and torrential rain are all risks, but will be hit-or-miss. Much more seasonal temperatures are expected starting Saturday, with daytime highs in the mid-to-upper 80s expected for several days.