BOISE, Idaho — WHAT/WHEN: A late-summer storm system moves through the region with unusually heavy amounts of monsoon moisture for the season. Heavy rain is expected to become more widespread in the overnight hours late Tuesday into early Wednesday, continuing into the afternoon.

Some areas in the Treasure Valley could see around a 0.25"-0.5" of rain, while mountain locations may get 1-2", but as much as 3" is possible. Even small amounts are significant as Boise normally gets less than 0.25" of rain for the entire month of August. The heaviest rain could cause flash flooding in steep terrain, burn scars, and even neighborhoods with poor drainage. Temperatures will also drop about 10° below normal, making Wednesday the coolest day of the week.

The National Weather Service has issued a

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