For years I have stored hundreds of 78s in my garage in the temperature ranges which are experienced in Southern Ontario - below 0 to over 90 degrees fahrenheit. There has never been any problems with these records, (although, as a rule, I never bring records indoors during the winter so they don't get a sudden temperature change). Two years ago, I acquired a large collection of 78s, between 40,000 and 60,000 records, and had to store them in three self-storage units, one indoor and two outdoors. A few weeks ago during a mild spell I dropped in on my main outdoor unit, (in which about 30,000 records are stored in steel cabinets), and was concerned to see the outsides of all the cabinets soaking wet with water running down in droplets. It appears that this was caused by condensation. When I opened one of the cabinets I saw that the insides were bone dry.
I'd be curious to know if anyone else has experienced this; these records also spent the winter of 2011/2012 in these outdoor units but they don't seem to have suffered any problems - last summer, any record I looked at in these units appeared and played just fine.