IOWA, USA — When winter turns to spring and summer in Iowa, there are some days where low levels of relative humidity and gusty winds prompt no-burn notices known as Red Flag Warnings.
Although Red Flag Warnings have been issued for the state 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."
In order to issue such a warning, the NWS says the following criteria must be met:
- 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.
During these times, any flame, burn or spark could burn and get out of control quickly. Outdoor burns are not advised and smokers should dispose of cigarette butts safely.
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.
