The Southwest Thermal Dome is expected to break dozens of altitude records

A dangerous heat wave in the west and parts of the south will threaten records over the next week as the heat dome intensifies and remains stationary over those areas. Sunday is expected to be the hottest day in years in some areas.

Here’s a look at the current temperatures:

Heat alerts are in effect for millions of people. The National Weather Service (NWS) has issued extreme heat advisories and warnings for more than a dozen states in the West and South. This means that outdoor activities should be limited in these areas either now or in the coming days due to the potential for heat-related illness.

Here’s how hot the weather will get early next week. Triple-digit temperatures will be steady across much of Texas into the Southwest and California (except near the coast and in the mountains). Parts of the desert southwest will be easily in the 110s, and even 120s in locations.

Phoenix reached 118 degrees on Saturday, breaking the highest daily record for the date.

Morning lows won’t offer much relief. Phoenix could see its temperature drop to just the low to mid 90s on several mornings over the coming days. Some spots may stay near 100 degrees overnight.

(More: Why are heat waves dangerous at night?)

The dome of high pressure will move eastward across the country’s southern layer during the central part of the week. This means that many other parts of the South will see increasingly high temperatures.

Daily records from Tuesday onward are likely from New Mexico into Louisiana and also into Florida. Albuquerque, New Mexico; Lubbock, San Antonio, Austin and Lardo, Texas; Baton Rouge, Louisiana; Tampa, Florida, could reach daily record highs.

Record temperatures expected. Many daily records will be threatened, but some all-time heat records are within reach.

Through Monday, daily record highs will be more numerous inland from California to Arizona, Nevada, Utah, New Mexico and western Colorado. Parts of south and central Texas will also approach daily record highs in the first part of next week.

Here are some additional notable people to approach.

-Las vigas: The city’s official all-time record of 117 degrees could be approached or tied on Sunday. Unofficial records indicate that the city’s temperature may have reached 118 degrees on July 26, 1931, according to weather historian Chris Burt.

-Death Valley: Highs in the mid to upper 120s are likely.

(more: Why is Death Valley so hot?)

-Reno, Nevada; Fresno, California; And Salt Lake City: Temperatures in all of these cities could reach within a few degrees of their all-time record highs of 108 degrees, 115 degrees and 107 degrees, respectively, Sunday through Monday.

How does a thermal dome contribute to rising temperatures? A strong high pressure area in the upper atmosphere is the main cause of this heat wave. Height causes air to fall toward the ground, compressing the air and making it warmer.

The heat dome in this case also delays the southwest monsoon from kicking in by preventing most of the moisture from entering the region from Mexico or nearby eastern Pacific waters. When seasonal humidity is present in the air, it can prevent extreme heat, although it also makes the atmosphere more humid and uncomfortable.

Here’s how to stay safe. Hot conditions will be particularly dangerous for vulnerable groups, such as the sick and the elderly. The NWS has helpful heat safety tips that can be incorporated into your daily routine when extreme temperatures occur.

-Work sites: Stay hydrated and take breaks indoors as much as possible. Remember, at temperatures above 110 degrees, you won’t know you’re sweating.

-Inside: Examining the elderly, the sick, and those who do not have air conditioning.

-In vehicles: Never leave children or pets unattended – look before you close the door.

-in the fresh air: Limit stressful activities and find shade. Drink plenty of water and avoid alcohol.

(more: 4 things extreme heat can do to your body)

Chris Dolce He has been a senior meteorologist at Weather.com for over 10 years after starting his career with The Weather Channel in the early 2000s.

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