An exceptional outbreak of extreme heat is set to engulf the West for much of the upcoming week, toppling records and bringing conditions that are extremely dangerous for some. Highs in spots could flirt with 120 degrees as sweltering temperatures exacerbate existing drought concerns and bolster the odds of a dangerous and deadly fire season. Nearly 40 million Americans could see highs in the triple digits, with hundred-degree heat extending all the way north to the Canadian border.

The heat could last for much of the week, its effects especially acute in the Southwest, before a pattern change this weekend. The record-setting temperatures predicted are made more likely in a world beset by human-induced climate change.

“A prolonged and record-breaking heat wave is underway across the western U.S.,” the National Weather Service declared Sunday.

That’s just the start of a string of days with records likely to topple across the West, and the Weather Service is urging hot-weather preparedness. Heat is responsible for more deaths than any other weather hazard in the United States in an average year.

Multiple Weather Service offices in the West have issued excessive-heat warnings for dangerously hot conditions, affecting more than 50 million people.

Triple-digit heat as far north as Montana on Monday

To start off the week, some of the most exceptional temperatures are in store for the northern portions of the Intermountain West.

On Monday, Billings, Mont., is forecast to hit 102 degrees, crushing the previous record for this day by four degrees. Billings is usually in the mid-70s at this time of year.