Brutal heat dome baking Mexico is heading for the U.S. What you need to know.

A prolonged and deadly heat wave in Mexico, one of the most extreme the country has faced, shows little sign of easing and is oozing into the United States, where it has already set records and fueled violent storms.

The heat has been breaking records in Mexico since early May. Many Mexican states have observed their highest temperatures on record, while more than 80 percent of the country is also enduring drought. Mexico City has set all-time record highs on multiple occasions, while fears grow that it may run out of water.

At least four dozen people have died of heat stroke and dehydration in Mexico over the past two months. And the heat is taking a toll on wildlife, too. Nearly 150 howler monkeys have died because of the high temperatures.