I think my hamsters died for the heat outside?

i put my 4 hamsters outside today because it was hot, i had 2 in one cage and 2 in the other,i went out to check on them and all 4 where dead. The temp was about 26 and the sun was shining, i was boiling out side. i took all of them out the cage and put then in a box for the rest of the day, then i buried them. i think they died from the heat? Please let me know as i want to get more hamsters but dont want the same to happed to them.