Summary of the Great Southwest U.S. Heat Wave of 2017
The great Southwest U.S. heat wave of 2017 is gradually diminishing, but it has left behind hundreds of smashed heat records, including at least four all-time hottest temperature marks for major stations. According to wunderground weather historian Christopher C. Burt, this week’s event has been the most intense heat wave yet recorded to affect the Southwest so early in the summer, coming about a week earlier than the previous great June heat waves that have affected the Southwest, like those of 2013, 1990 and 1994.
All-time hottest temperatures tied or broken during the heat wave:
Las Vegas, NV: 117° on June 20, tied the all-time record for the airport, which has a Period of Record (POR) back to 1937. However, there was a 118° reading measured by the official USWB COOP site on July 26, 1931.
Needles, CA: 125° on June 20, tied the all-time record. 126° was attained for a minute or two at one point, but not the 5-minute period needed to be deemed official. Previously, 125° was measured on June 20, 2016, and on July 17, 2005. POR: back to 1940.
Ocotillo Wells, CA: 124° on June 21, hottest temperature ever measured in San Diego County.
Prescott, AZ: 105° on June 21, tied the all-time record set on July 17, 1925. POR back to 1898.
Notable readings from June 18:
San Jose, CA: 103°, their hottest temperature since July 22, 2006, when it was also 103°. The last time it was hotter than 103° was on June 14, 2000, when the all-time San Jose record of 109° was achieved. POR since 1898.
Notable readings from June 19:
South Lake Tahoe, CA: 90°, tied for their hottest June monthly record along with June 25, 2015. All-time record for the site is 99° on July 22, 1988. POR only back to 1968. But this is, of course, a huge summer destination and keep in mind how a temperature like this at 6000’ is affecting the massive snowmelt now underway in the Sierra!
Notable readings from June 20:
Death Valley, CA: 127° (actually 126.5°, but rounded to 127°). This is the hottest temperature ever measured in the Western Hemisphere so early in the year.
Palm Springs, CA: 122°, 1° short of all-time record.
Phoenix, AZ: 119°, 3° short of all-time record, and the city’s 4th highest temperature on record. The extreme heat caused dozens of cancelled afternoon flights in Phoenix. As Dr. Marshall Shepherd explained in a Tuesday Forbes article, the cancellations were primarily due to the fact that air is less dense at hot temperatures. This results in less lift for an airplane, requiring a longer runway to achieve takeoff and a reduction in climb performance.
Tucson, AZ: 116°, 1° short of their all-time record. Their morning low of 87° gave Tucson an average daily temperature of 101.5°, their first triple-digit average temperature on record.
Reno, Nevada: 104° tied its all-time June monthly record set on June 16, 1940 . Reno’s all-time any month record is 108° set on July 10 and 11, 2002 and also on July 5, 2007. Reno has a long POR going back to 1893.
Tombstone, AZ: 110° tied its all-time June monthly record (along with three other earlier dates), and was 2° short of the all-time record of 112° set on July 4, 1989. POR since 1893.
Tonopah, NV: 102°, 1° short of the all-time June record, and 2° short of all-time record of 104° on July 18, 1960.
Thermal, CA: 123°, an all-time June monthly record, and 2nd hottest temp ever measured, following 126° on July 28, 1995. POR since 1950.
Notable readings from June 21:
Mexicali, Mexico: 51°C (123.8°F). According to weather records expert Maximiliano Herrera, this is the hottest reliably measured June temperature on record in Mexico. The only hotter temperatures in Mexico were measured in July 1995: 52.0°C (125.6°F) at Mexicali Sur and Rancho Williams, and 51.4°C (124.5°F) at Ejido Nuevo Leon (all located in Baja California near Mexicali.)
Winslow, AZ: 108°, tied its June record (also set on June 20, 2016). This fell just short of the all-time heat record of 109° set on July 13, 1971.
Notable readings from June 22:
Tucomcari, NM: 108°, tied as its 2nd hottest temperature on record (any month). Record is 109° set on June 21, 2013. POR since 1904.
Long streaks of record-breaking temperatures
The multi-day nature of this heat wave has been adding to it's dangerous nature: prolonged heat waves are especially hazardous because there is less chance for people to cool down by night, thus increasing the stress on those who do not have access to air conditioning. A few of the notable record streaks of hot weather from the heat wave:
Las Vegas, NV has seen 7 consecutive days of 110° readings, June 17 - 23. The Friday forecast for Las Vegas called for high temperatures of at least 110° through Monday. This would give the city ten consecutive days with highs of 110°+, tying the record set in 1961.
Redding, CA had five consecutive days that broke the record high for the date (June 18 - 22), with a peak of 113° on June 19th. POR since 1893.
Needles, CA tied its record for consecutive days of 120°+ on June 19 - 21. Previous such streaks: June 28 - 30, 2013 and July 16 - 18, 2005.
Flagstaff, AZ hit 90° or hotter on six consecutive days, June 18 – 23, which is the 2nd longest such streak on record.
Prescott, AZ hit 100°+ on five consecutive days, June 19 – 23, the second longest such streak on record. If it reaches 100° again on Saturday, it will jump into a tie for 1st place.
Winslow, AZ hit 105 °+ on four consecutive days, June 19 – 22, longest such streak on record. POR since 1898.