June is usually the hottest month of the year in the Southwest, but even by that measure, this year has been a stand-out. Record-breaking heat baked the region starting over the weekend thanks to an intense heat wave.

The peak of the heat wave was earlier this week, when new daily record highs were set in Las Vegas, Phoenix, Tucson, and Yuma. Death Valley, which is infamous for its heat, reached 126°F (52°C) on Monday, eclipsing the record of 125°F set in 1961. The all-time record there is 134°F (57°C), set on July 10, 1913.


Record highs were also set Monday in Palm Springs and Thermal, Calif., with both locations hotter than 120°F (49°C).

In Phoenix, nine of the first 22 days of June have been 110°F (43°C) or hotter, including the last five consecutive days. Periods of days over that threshold have been on the rise; of the five instances with 10 or more consecutive days at or above 110°F in Phoenix, four have come since 1989. The other was in 1974.

And the number of days each year above 110°F continues to climb there.

If the current trend in greenhouse gas emissions continues, there may be as many as 70 days each year hotter than 110°F in Phoenix.

110-degree days in Phoenix

Despite the hope that deserts can be cool at night, it has not been the case recently. The low in Phoenix on Monday was 90°F (32°C), which is the earliest in the year the low temperature has not dropped below 90°F. The hotter nights do not allow the body to recover from the heat stress of the daytime, increasing the risk of heat-related illnesses.

The heat has worsened efforts to fight wildfires in the Southwest, which is still mired in drought. Among the largest fires blazing right now is the San Gabriel Complex Fire in the hills east of Los Angeles. As of Wednesday morning, it had grown to an area of 4,900 acres and was only 15 percent contained. The progress of these wildfires and the fight against them can be followed on WXshift’s wildfire tracker.

While there may be some tiny easing of the heat this weekend, a large dome of heat-inducing high pressure will settle back over the Southwest next week, meaning no rain should be expected to break the heat or assist in fighting the wildfires for the foreseeable future.

This extreme heat also affects aviation. As temperatures rise, the space between air molecules increases, meaning the air is less dense. This lower density means there is less lift on an aircraft’s wing from below. As a result, a higher speed is required to produce the same lift needed for takeoff, and more ground distance is needed for both takeoff and landing. Additionally, once the aircraft is aloft, the decrease in lift means a slower climb.

One positive about the desert climate of the Southwest is that it is the sunniest location in the country. As a result, it is in an excellent location to take advantage of the sun to generate electricity.

Solar energy chart

Based on data from the National Renewable Energy Lab, the graphic above would imply that 5 square meters (about 6 square yards) of solar panels would produce enough energy to run an average central air conditioning unit for about 10 hours a day. While efficiency of the central air conditioning system and the size of the home certainly make a difference, it indicates the viability of solar energy as a residential power resource.

As the summer wears on, the annual monsoon circulation will ultimately bring in more cloud cover and sporadic rain to the Southwest, easing temperatures back from their current extremes. Even so, the outlook for the rest of the summer from NOAA’s Climate Prediction Center is for temperatures to remain above normal in the region.