Dport,
Check the recent topic... but no, there is no spike in temps of more than 1 degree at any time for me. I've seen 85 F this late Spring and no problem. The 5n1 read 89 however.
Today I checked my Atlas batteries, (normal energizer) and they had lost just a little power since installing them when I received my Atlas at the end of last Summer. Also we are expecting rain tonight, so cleaned the bird S**T out of the rain collector. Also checked the fan, took apart the bottom because I could not hear the motor, but it was running just fine. A nice fan blade system in there just above the thermo/hygro which is housed inside a fine mesh screen to keep the junk off the air sensor chip.