By Chris Dolce

Dangerous and potentially deadly heat will spread toward the Southwest this weekend while continuing to impact parts of the Plains and South.

Some cities have already received record-breaking temperatures this week:

• Columbia, Missouri, broke its old record high of 96 degrees (set in 1952) by reaching 99 degrees on Wednesday.

• Des Moines, Iowa, tied its old record high of 96 degrees (set in 1913) on Wednesday.

The most extreme heat in the coming days will be in the Desert Southwest where highs could climb to near 120 degrees, including in Phoenix, where it hasn't been that hot in more than 20 years. The National Weather Service in Phoenix said that heat of this magnitude in their area is rare, dangerous and deadly. Additionally, some cities in the Southwest may get within a few degrees of their all-time record highs for any calendar day in history.

Heat advisories, excessive heat warnings and excessive heat watches have been issued by the National Weather Service for parts of the Mississippi Valley, Plains and the Southwest.

An expansive area of high pressure in the mid-levels of the atmosphere that is taking shape from the central states into Southwest is responsible for the torrid temperatures. When this pattern occurs, the air sinks and warms and the result is very few clouds and extremely high temperatures.

Below are the details on the heat.

Desert Southwest: Hottest in 20+ Years For Some?

High temperatures in the 110s and possibly approaching or exceeding the 120s, will be common in the Desert Southwest starting this weekend and continuing into early next week. Not only that, there won't be much relief from the heat at night with lows staying in the 80s in some areas.

Here are a few notables about the heat, which could reach levels not seen in 20+ years in some locations.

Phoenix:

• There is a chance Phoenix could get near 120 degrees on Sunday or next Monday. Phoenix has not hit 120 degrees since July 28, 1995, when it peaked at 121 degrees. The all-time record high in the city is 122 degrees on June 26, 1990.

• Even if the 120-degree mark is not reached, it's likely Phoenix will set some daily record highs. The current standing daily record high temperature in the city Sunday, Monday and Tuesday is 115 degrees each day.

• Low temperatures in Phoenix will only drop into the 80s Sunday, Monday and Tuesday morning.

Tucson, Arizona:

• The temperature in Tucson has not been as high as 113 degrees in more than 20 years, last occurring in July 1995, according to the National Weather Service.

• It's possible the city could flirt with 115 degrees Sunday into Monday, which has only been reached or exceeded there four times dating back to 1894. The all-time record high in Tucson is 117 degrees.

Las Vegas:

• Highs in the 110s possible early next week, potentially challenging some daily record highs.

• Lows may only fall into the low to mid 80s early next week.

Albquerque, New Mexico:

• Highs in the low 100s are possible this weekend into next week. Daily record highs will be within reach.

The early part of the summer months (June-August) is when the Southwest typically sees its hottest weather. This is before monsoonal moisture arrives, contributing to the development of showers and storms later in summer.

100s in Southern California

Parts of Southern California inland from the coast will also see very hot temperatures this weekend into early next week.

• Highs downtown are likely to be in the middle or upper 90s on Sunday into Monday.

• Triple-digit heat is likely slightly farther inland in Anaheim, Ontario, Riverside and Pasadena.

San Diego Area:

• Inland valleys away from the coast, highs may push into the 90s or low 100s.

Interior Southern California Deserts:

• High temperatures will push toward the 110s this weekend and may even reach or exceed 120 degrees, including in Palm Springs and Imperial.

Plains, Midwest Heat

The expansive ridge of high pressure will also continue to bring widespread middle 90s to low 100s throughout parts of the Plains and Midwest at times into this weekend. Hot temperatures will also extend into the Southeast through late-week.

Heat index or the "feels like" temperature, will be in the 105-115 degree range for parts of the Plains and South.

Excessive heat warnings are in effect for northern Oklahoma and the Kansas City metropolitan area through Friday.

Heat advisories have been posted for portions of the central and southern Plains, along with portions of the lower and middle Mississippi Valley. This includes Little Rock, Arkansas and Dallas.

In some cases, daily record high temperatures will be within reach. Here are a few cities that may come within a few degrees of their record high for the day indicated.

Thursday: Colorado Springs (91 degrees); Paducah, Kentucky (98 degrees)

Friday: St. Louis (99 degrees); Springfield, Missouri (97 degrees)

Saturday: Alamosa, Colorado (90 degrees); Waco, Texas (99 degrees)

How to Prepare For Extreme Heat

This type of heat can be life-threatening for some, especially if you aren't adequately prepared. Remember: heat-related illnesses, such as heat exhaustion and heat stroke, are possible under these extreme conditions. If you are traveling with young children or pets, please do not leave them unattended in a hot vehicle.

The National Weather Service has issued some great heat safety tips.

• Drink before you are thirsty.

• Do not leave kids or pets in the car, even for a minute.

• Reduce time in the sun.

• Avoid strenuous activity; postpone outdoor activities.

• Seek air-conditioned buildings.

• Help the elderly, kids and pets stay cool.

• Keep window blinds closed.

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