Today is looking more like it will become the first 90 degree plus day of the year across much of southern Indiana and central Kentucky (Bowling Green already hit 90 yesterday). Forecast high temperatures across the Louisville metro look to range from 90 to 95 degrees, with most of the rest of the region forecast to stay around 90. Combined with relatively humid conditions in the afternoon, expect to see peak Heat Index readings top out in the 95 to 100 degree range.
The average first date for the highs to reach 90 in Louisville is June 1st, with the earliest "first date" being April 10th of 2011, and the latest being July 14th of 1915. For Lexington, the average first date is June 13th, with the earliest being April 24th of 1925 and the latest being July 23rd of 1965. A couple of years, in 2004 and 1974, Lexington never reached 90 degrees! For Bowling Green, the average is May 20th, with the earliest being March 22nd of 1907 and the latest June 26th of 1935.
With this being the first time to reach this level remember to take it easy if working outside, especially during the peak heating hours between 11 AM and 5 PM. Drink plenty of water, even if you do not yet feel thirsty, and wear lightweight, light-colored clothing to help keep cool.