Another dangerous heat wave is building across the West, peaking this weekend and persisting into the first week of August in what's been both a hot summer and year so far.

Here's where current western heat alerts are

The National Weather Service has issued various extreme heat watches, warnings and heat advisories in parts of the West, as the map below shows, including the L.A. Basin, Las Vegas, Phoenix and Salt Lake City.

These alerts mean extreme heat is forecast for those areas that could impact you if you spend too much time outdoors or in places without air conditioning.

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(MORE: What do heat alerts mean?)

How hot will it get?

We're forecasting daytime highs to top 115 degrees not just in the hottest desert locations, but also in Las Vegas and Phoenix for several days at least through the weekend.

Highs above 100 degrees are also expected in much of the Great Basin, Rockies and Northern Plains through the weekend, including Boise, Denver, inland areas of the L.A. Basin and Salt Lake City.

(MORE: Your weather app's most important heat numbers)

Daily record highs are likely throughout this heat wave in the areas shown in the map below, again from Montana to the Southwest.

Death Valley, North America's hottest place, may see highs approach 125 degrees during this heat wave.

(TRACK THE HEAT: Temperatures | Heat Index)

And evening temperatures won't provide much relief. Morning lows may only drop into the 90s in both Las Vegas and Phoenix.

How long will the heat last?

Some heat relief will arrive in the northern Rockies by Monday.

But for the Southwest and Great Basin, searing heat is likely to continue through at least the first week of August, if not a bit longer.

(MAPS: 10-day US highs and lows)

What you should do

- Heat is the No. 1 weather killer in the U.S., with hundreds of fatalities each year.

- Heat lingering into the night for several days in a row is dangerous for those without access to air conditioning, especially in the cores of larger cities.

- Check on family, friends, the elderly and those with chronic illness who live without access to air conditioning.

- If possible, avoid being outdoors for long in the peak heat of the afternoon.

- If you can't stay indoors in the peak heat, take frequent breaks, avoid strenuous activity, drink more water than usual and wear loose, lightweight clothing.

- This heat will also affect some popular national parks, including Yellowstone, Grand Teton, Bryce Canyon, Zion and Death Valley. If you're planning a visit and would like to hike, do so as early in the morning as you can.

(MORE: Affordable ways to keep cool during this heat wave)

It has been a record hot year

This heat wave is just the latest one in what has been a record hot year, so far, in the West.

Through July 28, it's been the hottest year-to-date in over two dozen cities from Texas to Arizona, Nevada to the northern Rockies, according to the Southeast Regional Climate Center.

That includes Las Vegas, Phoenix and Salt Lake City.

A late March heat wave rewrote state and national heat records in the West.

Summer heat has also not been kind to the West so far.

Phoenix has seen 12 days in July at or above 110 degrees. Las Vegas is not far behind with 10 days. Downtown Los Angeles has seen 9 days at or above 90 degrees this month.

Billings, Montana, Rapid City, South Dakota, and Sheridan, Wyoming also broke their all-time record highs earlier in July.