DES MOINES, Iowa — Much of western and central Iowa is under a Red Flag Warning from 12 p.m. to 9 p.m. Thursday.
Although Red Flag Warnings have been issued for Iowa many times in the past, they are less common here compared to states across the western U.S.
According to the National Weather Service, a Red Flag Warning means "critical fire weather conditions are either occurring now or will shortly."
Thursday's Red Flag Warning was prompted by a forecast of strong winds and low relative humidity, two factors the National Weather Service says contribute to extreme fire behavior.
Wind gusts will reach 40-50 mph across much of Iowa on Thursday, but it's possible some gusts will surpass 50 mph.
Relative humidity values in central and western Iowa will be less than 30% through much of the day, signaling just how dry the air is.
In order to issue a Red Flag Warning, the National Weather Service says they need the following:
- Ten-hour fuels of 8% or less. This parameter describes how much water is held by small vegetation such as grass, leaves, and mulch that take only about ten hours to respond to changes in dry/wet conditions.
- Relative humidity (RH) less than 25% for several hours. RH depicts how much water is in the air, relative to the temperature of the air.
- Winds 20 feet off the ground of at least 15 mph for several hours.
Red Flag Warnings are usually only issued during spring and fall fire weather seasons (Feb. 15 - Apr. 30 and Oct. 1 - Dec. 15), according to the National Weather Service.