I think much depends on your location and whether or not the garage is free standing, attached to or under the house? Do you have lots of humidity, or dry summers?
I would feel comfortable storing my sewing machines in my garage, but it is incorporated into my house, and about 1/3 underground. It can get quite warm, but not unreasonably so. Summers here can be hot, but not humid. The garage does not get as hot as outside.
Do you have any other options? Where will you be living for the two months? Is there a closet you can store them in, does a friend have a basement corner you can use?