JGalban via AviationKB.com wrote:



I think that could make the difference. According to the report, the fire
dept. measured the temperature at the site. Temps issued for weather reports
are taken in the shade under somewhat controlled conditions. They can differ
substantially from the absolute temperature measured on a hot ramp in the sun.


When the tower is reporting 110 degrees here in Phoenix, it's not unusually
for the plane mounted temperature probe (out in the sun, several feet off the
shimmering asphalt) to report temps in excess of 125 degrees.

John Galban=====N4BQ (PA28-180)




And several Mountain Flying books mention that specifically. The
official temperature anywhere is always in the shade. Ever seen a
runway in the shade?