Assuming you are talking about controller based, run "show ap tech-support" and eventually you'll see something like:
TEMPERATURE SENSOR: wl -i wifi0 phy_tempsense
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20 (0x14)
Fairly sure that is the measured temperature on the CPU.
For the outdoor APs, cold is usually only an issue if we are looking at a cold start. If the AP is already operating when the temperature goes to or beyond the published limit, the waste heat from the electronics will typically keep the internals of the AP within operating specs.
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Carson Hulcher, ACEX#110
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