When Mother Nature turns up the dial on heat in West Texas, temperatures can quickly soar above the century mark. It's times like these my Facebook page and twitter are flooded with people posting outrageous readings from their car or home thermometers. That's why I just wanted to set the record straight about the accuracy behind some of these instruments, so you know just how much you can trust them.
Here's the deal, it's not so much about the actual instrument as it is about WHERE it's placed.
For example, your car thermometer is usually not located very high above the ground. That means radiation from the HOT asphalt that can reach scorching temperatures is likely influencing the thermometer reading in your car.
While home thermometers, placed in the shade, are a little better in terms of accuracy, they're still not always spot on, especially in the heat. This is because the closer they are to your home, the more they will pick up on heat radiated off surrounding objects.
It's important to also note that "official temperatures," as recorded by the National Weather Surface ,are not always a true reflection of individual temperatures outside of your home. Temperatures can vary across cities and even towns, but these differences can be attributed to heat reflected off local buildings, areas with a lot of pavement or asphalt verses heavily shaded/wooded areas, and similar environmental variations. With that behind said, your car/home thermometer is not necessarily wrong, however when it comes to the temperature of the environment outside the common influences of buildings and roads, it is sometimes a gross exaggeration.
"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." (Click Here for more from the NWS)