What should I do before operating the cooling system on a cool day?
To avoid compressor damage, do not operate the cooling system when the outdoor temperature is below 50°F (10°C). Always check the compressor manufacturer's instructions for further information about safe operating temperatures.
From the official Honeywell CT3355 Home Programmable Thermostat manual, page 6
Have a follow-up question?
Answers from the official manual.
Common questions