Missing Monsoon Has Led to Growing Drought, Record Heat in Southwestern U.S.

 Linda Lam

Published: August 10, 2020

The monsoon in the Southwest has been generally inactive so far this year, which has led to an expansion of drought and record heat in the region.

The upper-level setup has not been ideal for ample rainfall to drench the Southwest or for heat relief to arrive this season, which lasts from June 15 through Sept. 30.

At this time of year, the area of high pressure is typically located in the southern Rockies or southern Plains, which allows plentiful moisture to flow into the Southwest from the Gulf of California and the Gulf of Mexico. This is not the situation that has taken shape recently.

This week, a ridge of high pressure over Mexico and the Southwest will center over Arizona and New Mexico. This setup is unfavorable for monsoon moisture to surge across the region. A wind flow from the west and southwest typically brings drier air over the region, and this is what is generally expected this week.

Setup This Week

Dry Conditions Prevail

A dry week is anticipated for most of the Southwest . As a result, drought conditions will likely worsen and expand.

At the start of June, about 14% of Arizona was in drought, but as of Aug. 4, 82% of the state is now experiencing drought conditions. It is a similar story in New Mexico where 95% of the state is now in drought, compared to 44% on June 2.

July and August are typically the wettest time of year for much of New Mexico and Arizona so it is worrisome to see dry conditions at this time of year. In addition, most of northwestern Mexico and the southwestern U.S. receive over half of their annual precipitation from the monsoon, so when the monsoon is a no-show it can impact reservoir replenishment, vegetation and wildfires.

Latest Drought Conditions

Many locations in southern Nevada, Arizona and southern Utah are experiencing one of the driest summers on record so far.

Las Vegas has not seen measurable rainfall since April 20 and is tied with several other years for the driest summer to date.

Cedar City, Utah, has recorded just 0.05 inches so far this summer, making it the driest on record. Phoenix and Tucson are both experiencing their fourth driest summer on record.

Most locations in the Four Corners region into Nevada and California have seen little to no precipitation in the first nine days of August. This dry trend will likely last through at least the first half of the month.

Rainfall from Aug. 1-9, 2020.

Hot Summer Continues

The monsoon usually brings relief from the scorching summer heat. However, with a generally absent monsoon, excessive heat can persist.

Several daily record highs and record warm lows are anticipated later this week and into the weekend from western Texas into Southern California.

Phoenix set a record for the number of days in a calendar year with a high temperature of at least 110 degrees. This year there have been 34 such days and that record will be added to this week. Highs are expected to be 10-15 degrees above average late this week and into the weekend, which corresponds to highs around 115 degrees.

Temperatures this hot can be dangerous and result in heat illnesses, including heat exhaustion and heat stroke. Signs of heat illness include confusion, dizziness, nausea, fatigue, heat rash and headache. Additional symptoms of heat stroke include high body temperature, change in sweating, rapid breathing and a racing heart rate.

If these symptoms begin it is important to get out of the heat, stay hydrated and rest. Seek medical help if heat stroke is suspected.

Dry and hot conditions also prevailed last year in the Southwest. The monsoon in 2019 was the ninth driest and third hottest on record for the region, since 1895.

It remains to be seen if this year will be different. The area of high pressure may shift westward this weekend over Arizona which would continue the dry trend. However, there are signs that changes may be ahead by the middle of next week which could result in a shift in winds and allow some monsoon moisture to return.

Overall, the hot and dry trend looks to persist in the near future. NOAA's Climate Prediction Center indicates that the Southwest has above average chances of experiencing warmer than average temperatures and drier than average conditions through the middle of August.

The Weather Company’s primary journalistic mission is to report on breaking weather news, the environment and the importance of science to our lives. This story does not necessarily represent the position of our parent company, IBM.

The Weather Company’s primary journalistic mission is to report on breaking weather news, the environment and the importance of science to our lives. This story does not necessarily represent the position of our parent company, IBM.