I didn't have any issues with this at all. What time is your ceremony? If it doesn't start until later on it won't be as hot out (ours started at 5:30 I think and I was fine, although it wasn't smokin hot to begin with because rain clouds had rolled in like 15 mins before).
I think you should be ok though. I didn't have a problem with my rings fitting, even when it was 90-95 degrees during the day!