(NEW YORK) — A swath of the United States is facing a dangerous combination of extreme heat and wildfire smoke this week.

More than 85 million Americans across 15 states — from California to Florida — are under heat alerts for Wednesday, according to the National Weather Service.

The consecutive days of record high temperatures combined with overnight temperatures remaining high makes this heat wave especially threatening. The longer it lasts, the more dangerous it becomes.

A number of cities are shattering records amid scorching temperatures.

Tuesday marked the record-breaking 19th straight day that the heat index value was at or above 110 degrees Fahrenheit in Phoenix, Arizona, with no end in sight. Overnight temperatures there also haven’t dropped below 90 degrees for a record nine days in a row.

In Miami, Florida, the heat index value has been at or above 100 degrees for a record 38 consecutive days.

El Paso, Texas, has counted a record 33 straight days with the heat index value at or above 100 degrees.

Las Cruces, New Mexico, has gone a record 17 days in a row with the heat index value at or above 100 degrees.

The heat wave isn’t expected to end anytime soon. The latest forecast shows above average temperatures for the rest of July, particularly in the West and the South.

The last 16 days on Earth have been the hottest on record and the planet’s surface temperature is on track to break a record set only a couple weeks ago.

Meanwhile, several states in the East are under air quality alerts due to smoke from raging wildfires in neighboring Canada. The smoke was expected to lighten up on Wednesday as the weather front moves through the region.

California is now battling its own wildfires, with heavy smoke drifting over cities such as Fresno and areas up the northern coast. Dangerous smoke was expected to spread into Medford, Oregon, on Thursday.

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