Red-flag warnings of dangerous wildfire risks are popping up across the US. Here's how to protect yourself if you see one.

• Red-flag warnings have been issued across the US, stretching from New Mexico to Massachusetts.
• The warnings go by many names and signal arid weather that can lead to rapidly spreading wildfires.

You may have seen the alert in the news or on your phone's weather app: red-flag warning. They've been more common in certain parts of the US, especially California, where scientists and officials now believe some parts of the state are in a year-round fire season.

But what do red-flag warnings mean? Red-flag warnings indicate dry, arid weather and strong wind conditions that increase the possibility of dangerous wildfires. Unlike a fire weather watch, which is issued 72 hours before conditions are ripening for a fire, red-flag warnings can be issued during a fire or up to 24 hours beforehand.

With the right winds and dry vegetative fuel, wildfires can spread quickly to burn down homes and even entire towns. In a single day in December 2021, a blaze in the suburbs of Denver and Boulder, Colorado forced 30,000 people to evacuate and destroyed nearly 1,000 homes.

Fires are burning more acreage across the US, over a longer fire season, than they did in the 1980s and 90s, according to government data. So it's no surprise that many parts of the country, from California to Colorado to Nebraska, are seeing more frequent red-flag warnings for fire weather.

As of Wednesday, nine states have issued red-flag warnings. One map shared on Twitter by climate reporter Dave Levitan shows the latest range of red-flag warnings stretching from New Mexico to Massachusetts.

Wisconsin Governor Tony Evers declared a state of emergency to free up wildfire response resources in light of the state's red-flag warning.

Why fire weather is a growing threat

Human activities have drastically altered the planet's climate, and therefore weather patterns, over the last few decades. By burning fossil fuels like coal and oil for energy, humans have released immense quantities of heat-trapping gases like carbon dioxide and methane into the atmosphere.

As a result, global temperatures are rising. Many parts of the world, like the western US, are becoming drier as a result. More extreme and extensive droughts, alongside higher temperatures and more frequent hot days, are a perfect recipe for wildfires.

As a result, fire seasons in many regions are getting longer and more active. Increasing fire weather in the western US is mainly driven by climate change, according to a 2021 study supported by the National Oceanic and Atmospheric Administration.

The most recent National Climate Assessment, released in 2018, projected an increase in wildfire risk in the Southeastern US, with a longer fire season and more land area burning from lightning-ignited fires. Increasing drought conditions are already causing larger, more destructive wildfires in the West.

Other factors, like overzealous fire suppression policies and overgrown forests, have contributed to an abundance of wildfire fuel in Western states like California.

What to do if a red-flag warning is issued in your area

If you're under a red-flag warning, check for burn bans in your area before you start any outdoor fires, don't leave fires unattended, and don't toss cigarettes on the ground.

To stay up-to-date on the weather, evacuations, and the progress of any fires that break out, follow updates from your local government and National Weather Service office.

Planning ahead is crucial to protecting yourself in the event of any disaster. It helps to have a "go bag" with food, water, first aid, medications, money, important documents, and other emergency supplies, in case you have to leave home in a rush.

Smoke from wildfires carries a host of health risks, so you can protect yourself by keeping N95 respirator masks at home and in your go bag.

You can prepare for any future evacuations by planning your evacuation route (and being ready to adjust it according to real-time official instructions), having a plan to take pets with you, and scanning important documents and storing them on a cloud service.

The US government website Ready.gov features step-by-step guides to prepare for any disasters, including wildfires.

You can check overall wildfire risk for your property using the online tool Risk Factor, developed by the climate-data nonprofit First Street Foundation.

Lastly, the NWS has some basic guidelines to avoid igniting fires during a red-flag warning:

• 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 3/4 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.