I would say no and this is based on purchasing not seeds but SPORES for mushroom cultivation which is far more sensitive to temps, Also this is 2014 most cars are AC equipped and my mail man tends to pull in the driveway with his on full blast.. As are most buildings temp controlled.. Remember usps ships alot of items including but not limited to live plants, animals, Fruits , veggies ect ect, Would be a bad business practice to let items spoil while in there control...
Anyway i don't think unless your leaving them in your mail box in the beating sun theres gonna be a huge impact.. Wiliam76 your issues could be related to summer breading from the breeder himself not the enroute issue.. It is summer all over 1/2 the world after all ;)