Boise, Idaho – Record-breaking heat is gripping southern Idaho as Boise, Caldwell, and Nampa climb toward 99°F on Thursday and Friday, with temperatures finally dropping by Sunday.
According to the National Weather Service in Boise, cities across the Treasure Valley—including Mountain Home and Ontario—will experience highs near or above 98°F through Friday, with triple-digit readings possible in Ontario. Residents in Baker City, Burns, and Idaho City will also see highs in the mid-to-upper 90s. A noticeable cooldown begins Saturday as highs fall into the upper 80s and lower 90s, and cooler air arrives Sunday into early next week.
The heat will be most dangerous during the late afternoon and early evening, especially in urban areas and along major roadways like I-84. Health officials urge everyone to limit outdoor activity, stay hydrated, and check on vulnerable neighbors. Schools and outdoor workers should plan for extra breaks and shade. Cooling centers are available in Boise, Nampa, and Caldwell.
This early-summer heat surge is the strongest since June 2021, and rapid temperature drops over the weekend may bring gusty winds and increased fire danger, especially in foothill and rangeland areas.
High temperatures will remain below 85°F for most locations by Tuesday, but additional advisories are possible if thunderstorms develop.
Five Day Idaho Weather Outlook
- Thursday: Highs 98-100°F (Boise, Caldwell, Ontario, Mountain Home). Dangerous heat risk.
- Friday: Highs 95-99°F. Slightly cooler west, heat persists Treasure Valley.
- Saturday: Highs 88-94°F. Notable cooling begins, winds increase.
- Sunday: Highs 80-91°F. Cooler, breezy. Fire risk in rangelands.
- Monday/Tuesday: Highs 79-85°F. Pleasant, potential for isolated storms.
