After a year of study, the National Weather Service has confirmed what people in Tucson, Ariz., had long suspected: The city's official thermometer runs too hot, by as much as two degrees on some days.
But the weather service also has established what only the skeptical would have believed: All of the government's new electronic thermometers in the Southwest also run too hot by about two degrees.
In Tucson, the electronic thermometer, the HO83, has been under suspicion since it was installed three years ago. Unlike the old liquid-and-glass thermometers, the electronic thermometer does not need to be monitored by meteorologishts because its observations are recorded automatically in a computer.
Last year, the electronic thermometer reported a string of records in Tucson, including an all-time high temperature of 117 degrees. It was at that point that the weather service moved to cool things off.
Joe Schiesl, a weather service official, said it sent teams around the country to compare readings of the HO83 with those of thermometers used at the National Institute of Standards and Technology.
A year later, the agency concluded that the electronic thermometers tended to overstate temperatures.
Mr. Schiesl explained that a mechanism in the thermometer designed to measure humindity often allowed air to remain trapped inside a chamber, where it was heated by the sun.
He said his office was trying to change the design so the air would be pushed quickly through the device to prevent it from heating up and that the changes would cost less than $1,000 for each thermometer.