A wildfire raging in Northern California has left 80 dead and upward of 1000 missing. And now, because of the smoke, many more people in the region are breathing in dangerous, smoke-polluted air.

You can see in the Environmental Protection Agency’s air quality monitoring map below how widespread the air quality problem is for the state. This map will auto-update every hour with the latest air quality measurements.

The brown shaded area is where the EPA says the air is truly hazardous. If you live in this area, the EPA recommends that “people with heart or lung disease, older adults, and children should remain indoors and keep activity levels low,” and that “everyone else should avoid all physical activity outdoors.”

On Friday, the air quality index in Sacramento was at 316. That’s hazardous. Breathing in that air for a day is roughly equivalent to smoking 14 cigarettes. Now it’s at 179, the equivalent of eight cigarettes.

A much greater swath of Northern California has “unhealthy” air, meaning everyone in the air may feel some effects of pollution. This area includes the densely populated San Francisco Bay region.

The air quality got a little better over the weekend, but the situation can change quickly. If you live in California, you should check back on the EPA’s Air Quality Index page for California (or our map above), and see what warnings and hazards are being listed by your local branch of the National Weather Service.

San Francisco Bay Area has had 10 continuous days of dangerously unhealthy air quality from the devastating November wildfires. This is an uncalculated cost of #climatechange. pic.twitter.com/NuwsJAm9tW — Peter Gleick (@PeterGleick) November 19, 2018

The problem with wildfire smoke is that the particles in it are so tiny, they can find their way into the smallest nooks and crannies of your lungs. Particles with a diameter of less than 2.5 micrometers (one micrometer is a millionth of a meter) factor heavily into the EPA’s assessment of air quality, and are a dangerous pollution component of smoke.

“These microscopic particles can get into your eyes and respiratory system, where they can cause health problems such as burning eyes, runny nose, and illnesses such as bronchitis,” the EPA warns. “Fine particles also can aggravate chronic heart and lung diseases — and even are linked to premature deaths in people with these conditions.”

People in these areas seeking protection from the smoke should consider N95 respirators or P100 masks. These face masks have filters that can block out most (but not all) of the pollution that’s smaller than 2.5 micrometers in diameter (often called PM 2.5).

Much of the smoke in Northern California is coming from the Camp Fire, named after Camp Creek Road in Butte County, where the blaze began. The fire is the most destructive and deadly in California’s history. One town of 26,000, called Paradise, burned down almost entirely. Sixty-three are dead, and the Sacramento Bee reports that more bodies are expected to be found.

Also unsettling: More than 1,200 people are still missing. The list is compiled from friends and relatives who have not been able to contact people living in the fire-stricken areas. “The level of chaos we were dealing with was extraordinary,” Kory Honea, the sheriff and coroner of Butte County, told the Bee. Many people had to flee their homes with not much time to prepare. Some people fleeing the fire have been displaced from a tent city set up in a Walmart parking lot, “and many of them are unsure of where they will go next,” the Chico Enterprise-Record reports.

Why did this happen? As Umair Irfan explained for Vox:

As climate change pushes temperatures up, vegetation like grasses and trees are dying out. This creates ample fuel to burn. Outside of Chico, where the Camp Fire began burning, the flames were then fanned by northern California’s Diablo Winds with gusts topping 70 mph. The fire at one point gained about a football field in area per second. Though the Camp Fire resulted from a perfect set of extreme fire conditions that all coincidentally came together at the same time, some of those conditions were years in the making. It’s an example of how forces in the climate that build up over decades can act on the scale of days, even hours, creating a terrifying scenario the likes of which we have never experienced before.

Around 150,000 acres, or 234 square miles total, have burned in the blaze, and it’s only now 65 percent contained. (There are also fires burning in Southern California. More on those here.)

Forecasters are hoping that a change in the winds and a chance of rain next week will help contain both the fire and the smoke. Here’s a forecast map for the smoke that will update in real time. But for now, it’s dangerous out there.