With St. George tying record for hottest day, what does it take to show a proper temperature reading?

Stock image | Photo by Xurzon/iStock/Getty Images Plus, St. George News

ST. GEORGE — It happens every year: The outside temperature is at or approaching record levels, and car thermometers and home weather stations show outlandish temperatures like 125-140 degrees. With St. George unofficially tying a previous record of “only” 117 degrees over the weekend, it’s evident that there is a lot more that goes into obtaining an accurate reading than consumer thermometers can provide.

Close up of car dashboard showing an inaccurate temperature reading of 120 degrees. July 11, 2021 | Photo courtesy of Cynthia Wayman, St. George News

So what does it take to have a temperature reading that would be acceptable for a record? The National Weather Service has a network of weather observers, called COOP observers. These volunteers have a high standard that they must follow in order to maintain their standing with the NWS.

First off, there are only three types of electronic equipment that are acceptable to the NWS. One of them is no longer being made, and none of the three can be bought at a local big box store or online. Second, the sensor must be mounted in a shelter, and instructions for mounting the sensor are very strict, including the following guidelines:

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.

Third, the NWS provides observers with calibration equipment, and the sensor must be calibrated every 6 months or when requested. This is to assure that readings are not being affected by direct sunlight, ground radiation or asphalt/concrete radiation.

Even with all of these strict guidelines in place, the weather service isn’t ready to proclaim Saturday’s reading of 117 degrees Fahrenheit as official. Meteorologists are looking at the data and have yet to say if the temperature can reasonably tie with the record of 117 degrees previously set in 1985.

Think you would like to join the NWS network? Here are some of the things you must do before you can be accepted in the program.

Copyright St. George News, SaintGeorgeUtah.com LLC, 2021, all rights reserved.

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