Hmmm you're getting very close to the maximum rated temp range specifications "-30°C to +60°C (-22°F to +140°F)"
ePMP AP radios use more power when it's cold to power a small internal heater. Depending on the PoE, power supply, and cable length and guage used, you may need to supply it more power.
Please see THIS article on operating ePMP radios in sub freezing tempuratures.