Seasonal HVAC tune-up reminder email before the first heat wave

In late April, email everyone who's had an HVAC service call in the past two years, reminding them that a pre-summer tune-up can catch problems before the first hot week and linking to your online booking calendar. Repeat the same email in October for heating systems.

Why it works: Reaching customers before the season's first extreme weather beats competing with everyone else once the heat or cold actually arrives.