I've done lager fermentations outdoors before, to take advantage of the seasonal temperature drops.
This should work assuming daily outdoor (or garage or cellar) temperatures are at 50F or less. I have a 30G rubbermaid trash can that I fill about halfway with water. Then, I lower a carboy with fresh wort into it, careful to make sure it is stable and not floating in the can. I have an inexpensive temperature controller that I put its probe into the liquid, and connect it to a 100W fish tank heater. I carefully put the lid onto the trash can to keep birds and crap from falling into the trash can. I dial in the temperature controller to start heating at about 50F.
The extra thermal mass of the carboy+trash can water help moderate daytime/nighttime temperatures, and the heater helps keep everything from getting too cold at night. I did this in March and saw outdoor temps between 40F-58F during the day, and probably down to 20F or close to it at night.
Its sort of an experimental thing, but it is cheap to put together. I haven't decided if having a mini-fridge would be more economical to maintain the 50F inside instead after $70 in trash cans, heaters, temperature controllers...etc.