Wednesday, June 24, 2009

The bank says it's 107... and my car says 115!

With all the record heat over the past week, there's been a lot of people very interested in the air temperature. Nowadays, there's thermometers everywhere...our cars, the bank, plus a lot of personal weather stations that are linked together online. Many of these thermometers have readings that are very high when compared with the National Weather Service gauges. Some folks have told me that a bank say it's 107 degrees outside and their car says it's 115! Meanwhile, the NWS gauges are only reading 100 degrees.

So what gives?

Well the NWS puts its sensors in locations away from re-radiated heat. Sensors are solar-shielded and located at least ten feet away from trees, fences, buildings, concrete and asphalt.

Bank thermometers are usually inside a metal case which sit in direct sunlight. So the temp inside the box often gets hotter than the actual air temp.

All cars are not the same, but most car thermometers contain basically the same ingredient as a sophisticated weather station: a thermistor. However, these sensors are close to engine heat as well as re-radiated heat from the concrete and asphalt roads.

Sometimes people mount their thermometers on there roof or in direct sunlight, which is another reason you may have an inaccurate reading.

So it's fair to use your car and the bank to get a ball park reading, but it's probably best to trust the National Weather Service if you want a true reading. Here's a link to the conditions at the local airports.


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