An intense heatwave is crippling the West this week, sending the mercury above 120 degrees F in places like Phoenix. In a sign of just how hot things are getting, some airlines have had to cancel flights because of the heat.

American Airlines said it canceled 50 flights out of Phoenix Sky Harbor aboard Bombardier CRJ aircraft on Tuesday because the planes can’t operate above 118 degrees F.

Heatwaves are intimately tied to climate change as rising background temperatures make them more intense and common. The latest batch of heat will cook an area from northern California to western Texas, a region home to some seven of the 10 fastest-warming cities in the country.

Temperature records have already fallen across California and heat will build throughout the week. Sacramento, San Jose, Palm Springs, Fresno, and Death Valley all set daily highs on Monday. But the hottest temperatures aren’t even expected to arrive until Tuesday. They’ll last through Thursday, and forecast highs mean the region could set all-time records.

Phoenix, Tucson, and Las Vegas are forecast to be within striking distance of all-time records. All eyes will be on Phoenix, which is ground zero for the heatwave. Temperatures are forecast to climb to 120 degrees F on Tuesday, just 2 degrees F shy of its all-time record.

All-time record hot or not, the extreme weather has the potential to…