An HVAC system includes a controller configured to receive weather forecast information including anticipated future outdoor temperatures. Based at least in part on the weather forecast information, the controller determines that test-initiation criteria are satisfied for testing operation of the HVAC system in a test mode. In response to determining that the test-initiation criteria are satisfied, the controller determines that current weather conditions are suitable for operating the HVAC system in the test mode for a test time period. The HVAC system is operated in the test mode for the test time period.