Health warnings have been issued across parts of the US on Thursday, with officials urging residents in affected areas to stay indoors if possible.
Federal data shows pockets of unhealthy air quality emerging in Oregon, Arizona and Georgia, alongside widespread moderate pollution across much of the country.
Air quality maps show elevated levels of PM2.5, microscopic particles small enough to penetrate deep into the lungs, creating hazardous conditions, particularly for people with respiratory conditions such as asthma.
These particles are typically produced by vehicle emissions, industrial activity and burning wood, and can trigger inflammation, breathing difficulties and other health issues when inhaled.
In southern Oregon, near the town of Chiloquin, air quality has reached unhealthy levels due to smoke from controlled burns, with pollution trapped near the ground by a temperature inversion that prevents it from dispersing.
In southern Arizona, including areas near Tucson, blowing dust from dry desert soils is driving similar spikes, as strong winds lift fine particles into the air and combine with emissions from traffic and construction.
Although major metro areas like Phoenix remain mostly in the moderate range, localized surges are pushing some neighborhoods into unhealthy territory.
In the Southeast, particularly around Atlanta, pollution is being driven primarily by ozone, which forms when emissions from vehicles, power plants and industry react in sunlight as temperatures rise.
Air quality maps reveal elevated levels of PM2.5, microscopic particles small enough to penetrate deep into the lungs, creating hazardous conditions, particularly for people with respiratory conditions such as asthma (STOCK)
Across parts of Kansas, Missouri and Oklahoma, smoke from seasonal agricultural and prescribed burns has created another cluster of hot spots.
These fires are common in the spring and are used to manage land, but the resulting smoke can travel long distances and linger, especially under calm weather conditions.
Officials stressed that the situation is not a nationwide emergency, but rather a series of localized pollution events tied to seasonal conditions.
However, residents are advised to limit prolonged outdoor activity, especially strenuous exercise, as air quality fluctuates.
Sensitive groups, including children, older adults and those with heart or lung conditions, are urged to avoid extended time outside during peak pollution periods.
Experts also recommended keeping windows closed, using air conditioning on recirculate mode and running HEPA air purifiers where possible to reduce indoor exposure.
The poor air quality comes as a historic heatwave is sweeping over the Southwest, triggering alerts for millions to stay indoors until 8pm local time on Friday.
The extreme heat warning covers Southern California, as temperatures are expected to reach 104 degrees Fahrenheit in some areas.
In southern Arizona, including areas near Tucson, blowing dust from dry desert soils is driving similar spikes, as strong winds lift fine particles into the air and combine with emissions from traffic and construction.
In the Southeast, particularly around Atlanta, pollution is being driven primarily by ozone, which forms when emissions from vehicles, power plants and industry react in sunlight as temperatures rise
In Los Angeles, millions are expected to bake under temperatures in the upper 90s, and the forecast may challenge the record for the earliest 100-degree day in the city since April 4, 1989.
The National Weather Service (NWS) has warned the public to stay indoors during the hottest parts of the day this week, and also to take frequent breaks in the shade or in air conditioning if you have to be outside.
Similar warnings have been issued in Nevada and Arizona, where this week’s temperatures are projected to be 30 degrees above normal for mid-March and will likely break records for 100-degree days, which have lasted for decades.
In both Las Vegas and Phoenix, extreme heat warnings have been issued for the next five days, spanning from Wednesday through Sunday.
The forecast has been caused by a massive ‘heat dome’ forming over 14 states, including California, Nevada, Arizona, Utah, New Mexico, Colorado and Wyoming.
A heat dome works like a high-pressure lid. It builds overhead, trapping hot air at the surface level, suppressing clouds and intensifying sunlight.
A spokesman for NWS warned: ‘There is a high risk for dangerous heat illness for anyone, especially for the very young, the very old, those without air conditioning, and those active outdoors.’
The agency added that the millions living under the heat dome will need to watch for signs of heat exhaustion or heat stroke.
Heat exhaustion often starts with heavy sweating, fatigue, developing cool, pale, clammy skin and a fast, weak pulse, muscle cramps, dizziness, nausea and headaches.
In southern Oregon, near the town of Chiloquin, air quality has reached unhealthy levels due to smoke from prescribed burns, with pollution trapped near the ground by a temperature inversion that prevents it from dispersing
As for heat stroke, which is far more deadly and can develop within 15 minutes in extreme conditions, the first symptoms are often a throbbing headache, confusion, slurred speech, nausea, dizziness, and a fever above 103 degrees Fahrenheit.
Sufferers may also develop red, dry, or damp skin, a rapid pulse, and lose consciousness.
Move anyone affected by these conditions into a cool, shaded spot right away and call 911.
Parts of Oregon, Idaho, Montana, Nebraska, Kansas, Oklahoma and Texas will also be affected, with meteorologists from AccuWeather warning that March temperatures, which are usually in the low 70s, could surpass 90 for several days.
