* WHAT...Temperatures up to 104 expected. Overnight lows will cool into the 60s and low 70s in the affected area, which is 10 to 15 degrees above normal for the time of year.
* WHERE...Challis/Pahsimeroi Valleys, Lost River Valley, Wood River Foothills, Beaverhead - Lemhi Highlands, Teton Valley, Eastern Magic Valley, Shoshone/Lava Beds, Arco/Mud Lake Desert, Bear Lake Valley, Lower Snake River Plain, Raft River Region, and Upper Snake River Plain.
* WHEN...From midnight tonight to midnight MDT Saturday Night.
* IMPACTS...Hot temperatures may cause heat illnesses such as heat exhaustion and heatstroke.
* ADDITIONAL DETAILS...Elevations below 5500 feet, the Teton Valley, and the Bear Lake basin are the areas most affected.