What Arizonans should know about red flag warnings

Red flag warnings in Arizona signal an increased risk of wildfire danger as temperatures increase, winds whip up and humidity drops.

The warnings are issued to alert fire managers on federal lands to expect conditions that allow fires to develop and spread rapidly, according to the National Weather Service.

Criteria for a red flag warning include a relative humidity less than 15%, warm temperatures and high winds for several hours, combined with dry vegetation in an area, the weather service said.

On Tuesday, the weather service in Phoenix issued a red flag warning from 2 to 8 p.m. due to high fire danger for most of the south-central and southwest portions of the state.

"It will be warm, windy, and very dry later today leading to very high fire danger. Red Flag Warnings in effect. Another round of dry and windy conditions Thu-Fri," the weather service tweeted.

Humidity is expected below 5% with winds from the west at 15 to 25 mph and gusts up to 35 to 40 mph. "Fuels are dry and fire danger is very high," the tweet stated.

The weather service advised:

If you are allowed to burn in your area, all burn barrels must be covered with a weighted metal cover, with holes no larger than three-quarters of an inch.

Do not throw cigarettes or matches out of a moving vehicle. They may ignite dry grass on the side of the road and become a wildfire.

Extinguish all outdoor fires properly. Drown fires with plenty of water and stir to make sure everything is cold to the touch. Dunk charcoal in water until cold. Do not throw live charcoal on the ground and leave it.

Never leave a fire unattended. Sparks or embers can blow into leaves or grass, ignite a fire, and quickly spread.