Weather Words: Red Flag Warning

Red flag warnings are a life-saving warning issued by the National Weather Service, and we aren’t talking about the red flags that are flown at the beach (which are also a life-saving warning system).

A red flag warning is issued when low humidities and dry conditions are present, along with very gusty winds. The combination of these three ingredients can lead to the development of wildfires, which can spread rapidly.

When a red flag warning is issued, it’s extremely important not to throw a cigarette butt or matches on the ground. A tiny spark can result in a raging wildfire. Even a spark caused by a loose chain or object dragging behind your car can ignite a wildfire.

Red flag criteria is generally when relative humidity is at 15% or less, combined with sustained winds and/or gusts of 25 mph or greater. Both of these conditions must occur simultaneously for at least 3 hours in a 12 hour period, according to the NWS.

Red flag warnings should be taken seriously and always make sure you have a way to get alerts in case a fire were to break out near your location and you are ordered to evacuate. Make sure you always listen and obey instructions from officials - it could save your life.

This segment originally appeared in today's edition of the Morning Brief newsletter. Sign up here to get weekday updates from The Weather Channel and our meteorologists.

J​ennifer Gray is a weather and climate writer for weather.com. She has been covering some of the world's biggest weather and climate stories for the last two decades.