Three days of late summer heat will settle into the region starting Sunday. According to the National Weather Service, daytime highs will jump into the 90s through Tuesday, with heat index values to likely exceed 100 in the afternoon and evening hours. The warmest day in the forecast is Monday. Those with outdoor plans should limit extended activities and take frequent breaks in air conditioning. A slight cooldown is expected by Wednesday, but highs will still hover around 90 for the better part of the week before a likely drop into the upper 70s and low 80s by Friday.