More than 21,000 electricity customers are without power in the Denver area and northern Colorado after a powerful wind storm.

Xcel Energy says the blackouts affected about 50,000 customers in Denver, Fort Collins and Greeley starting at 10 p.m. Tuesday. Crews restored service to most by mid-day Wednesday.

The company expects to have everyone online Wednesday afternoon.

The National Weather Service expects sustained winds of 25 to 40 mph with gusts of up to 60 mph possible across eastern Colorado Wednesday.

The wind and low humidity prompted forecasters to issue a red flag warning for eastern and southeastern Colorado, meaning the danger of fire is very high to extreme.