When someone mentions air conditioning, I think of small window units. Units range in size from small window units to units larger than a house. A typical HVAC-R technician will work on air conditioning and refrigeration units all year, even in the winter.
Many commercial buildings require cooling all year round.
Supermarkets need refrigeration to keep their produce fresh even in the winter. All houses and most commercial buildings require some type of heating units. The associate's degree from Hudson Valley Community College is all that is required. Some students with the time and resources do go on to four-year colleges, but this is not a requirement for success. Presently it is a male-dominated field, but that is slowly changing.