Scorching temperatures are in store for the southwestern U.S. over the next several days, with cities like Phoenix, Las Vegas and Palm Springs in California expected to top 110 degrees.

Parts of New Mexico and Texas also will see triple-digits.

Heat is part of the normal routine of summertime in the desert, but weather forecasters say that doesn’t mean people should feel at ease. Excessive heat causes more deaths in the U.S. than other weather-related disasters, including hurricanes, floods and tornadoes combined.

“Though weather conditions are going to be nice, you have to limit your outdoor activities significantly,” said Gabriel Lojero of the National Weather Service in Phoenix.

The temperatures forecast from Wednesday through Monday are the highest yet this year. Scientists say more frequent and intense heat waves are likely in the future because of climate change and a deepening drought.

The effects of spiking temperatures are felt most acutely among vulnerable populations, including people without homes and workers who labor outside. Homeless people are about 200 times more likely to die from heat-associated causes, said David Hondula, a climate scientist who leads the city of Phoenix’s Office of Heat Response and Mitigation.

At least 130 homeless individuals were among the 339 people who died from heat-associated causes last year in Maricopa County, which includes Phoenix, and has the highest population of any county in Arizona.

Phoenix already is considered the hottest big city in the United States. A heat wave last summer pushed temperatures up to 118 degrees (48 Celsius).

Most everyone in central and southern Arizona, southern Nevada and southeast California will be at risk for heat-related illness if they don’t take proper precautions, Lojero said. Those include wearing light-colored clothing, staying hydrated and seeking shade if they need to go outside.

Temperatures are expected to tie or break records, even at night when it’s cooler, before dropping overall early next week.

Phoenix and Yuma are forecast to be just shy of 115 degrees (46 C) on Saturday when the heat peaks across the region. Blythe and El Centro in California will be at or above that temperature. Las Vegas will top out at 111 degrees (44 C) during the heat wave, the National Weather Service said.

Phantom Ranch at the bottom of the Grand Canyon also will see triple-digit temperatures — a reminder that the weather changes drastically from the canyon’s rim to its inner depths. Heat was a factor in the June 2 death of a woman who was hiking back up the popular Bright Angel Trail after reaching the Colorado River the same day — something the park advises against doing, especially during the hottest times of the day, said Angela Boyers, the chief ranger.

Some places in New Mexico also are expected to see temperatures that could break records over the weekend. Thunderstorms over the next couple of days could cause flash flooding in areas that have been scorched by wildfire, forecasters said.

While temperatures had cooled this week in Texas, the heat is building through the weekend.

The sizzling numbers come ahead of the annual rainy season in the Southwest, known simply as the monsoon, that starts in mid-June and runs through September. Weather experts say the phenomenon has equal chances of being above, below and normal this year in Arizona.