ST. GEORGE — The debate about whether the reading of 117 degrees Fahrenheit in St. George on July 10, 2021, ties the all-time record has been about as hot as the temperature recorded that day.
But it’s time to douse the flames, thanks to the National Weather Service.
“After an exhaustive review, the State Climate Extremes Committee has verified St. George tied a new all-time state temperature record of 117F on July 10, 2021,” according to the NWS Twitter feed. “The previous record was set in St. George on July 5, 1985. Both records occurred within 2.58 miles of each other.”
For a time, it was believed 118 might have been the new record, but the committee report revealed an equipment snafu produced an unreliable result.
A temperature of 118°F was recorded south of St. George near the Arizona border on 4 July 2007. This was recorded at a now decommissioned Remote Automatic Weather Station (RAWS) site located at the Port of Entry along I-15 just north of the Utah/Arizona border. The equipment was determined to be insufficient to support a record of this magnitude by a committee in 2007.
The debate about the 2021 reading of 117, however, began after several non-NWS sources reported 118 on July 10. But the state committee convened several times since then and rendered an official decision June 27.
“After considering the validation of the equipment, surrounding observations and the meteorological scenario, the members of the SCEC voted 5-0 to accept the observation taken at the SGUU1 (St. George) COOP station site as tying the official maximum temperature record for the State of Utah,” the memorandum said.
As reported July 12, 2021, by St. George News, the NWS says obtaining a reliable measurement is, in fact, an exact science.
The sensor should be mounted 5 feet +/- 1 foot above the ground. The ground over which the shelter [radiation] is located should be typical of the surrounding area. A level, open clearing is desirable so the thermometers are freely ventilated by air flow. Do not install the sensor on a steep slope or in a sheltered hollow unless it is typical of the area or unless data from that type of site are desired. When possible, the shelter should be no closer than four times the height of any obstruction (tree, fence, building, etc.). The sensor should be at least 100 feet from any paved or concrete surface.
The specific locations of the weather stations are shown on the accompanying map.
According to the report, the July 10, 2021, reading came amid a heat wave that impacted Southern Utah and was the result of several factors.
“St. George and southwestern Utah had received little to no rainfall through most of the spring and into early summer,” the report said. “Temperatures had exceeded 110°F for four days prior to the record, with a high temperature the day prior of 116°F. The minimum temperature on the days preceding the temperature record ranged between 81–82°F (approximately 10°F hotter than normal minimum temperatures for this time in July), indicating minimal nocturnal cooling.”
And while the record-tying temperature reading from about one year ago appears to be safe for now, Southern Utahns are enduring yet another heat wave. Thursday’s official high was 100. And as of 4:35 p.m. Friday, the high had reached 104, according to the NWS.
This data comes from a weather station at St. George Regional airport (Latitude: 37.0451°N, Longitude: 113.50561°W, Elevation: 2,872 feet).
Add to that winds reaching 20 mph and daytime relative humidity ranging from 10-12% and no precipitation expected for the foreseeable future, and the resulting Red Flag Warning issued Thursday should come as no surprise.
Still, forecasted highs for the St. George area range 101-106 through Thursday, with lows expected 73-78. Cedar City, however, could see thunderstorms over the next seven days, with highs in the low 90s and overnight lows in the mid 60s, according to the NWS.
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