Contrary to popular opinion of those that have been doing this longer then me but my brewing experience leads me to agree with the OP. I recently had a similar issue (my AC worked, just not that well), I wasn't checking my storage closet as I should and discovered that it had been 95+ for maybe a week at a time shortly after I bottled. I am not sure when bottles started blowing but I found that a newer batch had 2 broken. I had three different batches recently bottled in there and at least 3 others that were up to 3 months old. All my priming sugars are added in the same fashion, 3/4c boiling water to dissolve, cooled, added to bottle bucket and beer racked in a whirlpool over it.
All FG tested for 3 days.
(New Ones about 2 weeks in the bottle)
Bass Clone (Extract)- OG-1.044 FG-1.011, 4 oz corn sugar, Primary for 10 days, Secondary for 18 days
Dunkelweizen (PG)- 1.046-1.010, 4.5 oz corn sugar, Primary-21 days
Sweet Stout (AG)- 1.055-1.014, 4 oz corn sugar, Primary 28 days
(Old Ones)
California Steam (PG)- 1.050-1.011, 5 oz corn sugar, Primary 7 days, Secondary 14 days, Bottled 12 weeks
Dunkelweizen (PG)- 1.048-1.011, 4.5 oz corn sugar, Primary-21 days, Bottled 8 weeks
Strawberry Blonde (AG)- 1.042-1.010, 5 oz corn, Primary 28 days, bottled 5 weeks
I can guarantee absolute sanitation, I work in the medical field and was a surgical assistant for 2 years.
Over the course of the next week or so I did some experimentation. I first moved some bottles around my house. Two of each kind went the the following places: refrigerator, kitchen counter, and hallway with the closet. The rest remained in place with the door closed.
My results were another couple broken bottles in the closet after 2 days, so I cracked the door. 3 days later broken bottle in the closet again, this time I put a fan in the door way blowing in. No other bottle busted and the closet ones stopped after I added the fan. All the beers tested were WAY over carb-ed, I mean I get about 6-9 oz. out of one bottle and have to open it 10 minutes in advance for the foam to die down. Bottles that came out of the closet when I first made the find seem to have more beer remaining after all the foaming (the most coming from the ones in the fridge). This effect happened across all my beers not just the freshly bottled ones.
My conclusion was the higher temps caused the yeasts to get a bit more active then they should have (even bringing some out of dormancy.) Which makes sense because highly active yeast ferment at a faster less efficient rate so we make efforts to ferment at lower temps to prevent off flavors. This faster less effective rate of consumption produced more CO2 then desired. Also to a possibly minor point if the excess CO2 pressure had my bottle at near the bursting pressure an increase in temperature would mean an increase in pressure (Boyle's Law) causing the explosion.
Need less to say with in a week have a shiny new (at least to me) fermentation chamber / bottle refrigerator. Good luck to the OP, it sucks to loose good beer.
