Summer "officially" started with the solstice on this past Thursday, but we had summery weather in the Midwest far before that. When summer started, we were getting a break from the heat and humidity with clouds and some drier air. Now the heat is going to get cranked back up.
Temperatures will be near average Monday afternoon, in the 70s and 80s... but it will feel warmer with high humidity.
Dew points in the 60s and 70s will make it feel sticky... and means there is sufficient moisture for showers and thunderstorms. A warm front will be lifting north to near I-80 during the day Monday. This will be the focus of showers and storms Monday afternoon, then the cold front associated with the system will sweep through Tuesday and bring in a second round of storms.
Because of the showers and storms ongoing Sunday evening, there is some uncertainty on the strength of the storms on Monday. Due to the proximity of instability in the atmosphere and the proximity of the warm front, there is the potential for some strong storms. The higher chances will be near and south of I-80 where there could be strong winds and hail in some storms.
Depending on where the front sets up is where the highest chances for strong storms will be. If rain and/or clouds linger too long Monday morning, instability may be lower. Additionally, timing of the arrival of the warm front could impact the strength of the storms.
It's going to be a similar situation Tuesday as storms linger into Tuesday morning, but once again there's the potential for strong storms.
There could be decent rainfall, too, over the next two days.
Summer returns with heat, humidity and thunderstorms this week. Temperatures will be warming back into the 80s and 90s with heat index values near 100, especially during the end of the week.