I went shooting yesterday afternoon when it was a nice, cool 106 degrees. The Blazer ammo I had with me did not show any signs of wax melting and it sat in an ammo can in the cab of the truck for most of the time I was at the range.
Having said that, I do not mail order any .22 ammo during the summer time because I have had CCI standard velocity arrive with the lube melted. Luckily the ammo was oriented so that the bullet was facing down and the melted wax formed a small blob on the tip of the bullet. Some were stuck to the box. When it came time to shoot it I simply used my fingers and smeared the blob around on the bullet. No issues with accuracy or leading.
My son left an ammo can of .45acp that was reloaded using cast lead SWC's that were lubed with blue wax in his car for an entire summer in Phoenix. Some -not all- of the wax melted out and coated the outside of the brass and stuck the cartridges to each other and the sides of the box. I pulled a few bullets and found that there was still wax in the lube ring and the powder was not contaminated. I wiped the wax off of the cases with a rag and shot a few.....no accuracy issues, extremely minor leading that came out easily with a brush. All of that ammo has now been shot with no issues.
Short version: put it in a cooler and press on. If the wax does soften and melt, a little rub-rub-smear-smear as you use it will take care of the problem.
On the subject of ammo exposed to heat, here are two short stories of personal experience:
My house burned down about 20 years ago. The ammo was in the garage and not directly exposed to the fire, but it was only one interior wall away. I'm pretty sure it got a bit warm. All of it was fired with no issues.
A few years after the house was rebuilt, my neighbor asked me if I wanted her deceased husbands reloading stuff. Mixed in with the boxes that had been stored in an outdoor metal shed in Phoenix for at least 10 years was a few pounds of Alcan AL-7 (think about how long that's been discontinued) and CCI primers in the old tan boxes with the red/white CCI logo. I researched some old reloading manuals and found a .38 special load that would said it would produce 800fps with a 158 LSWC. I loaded them up and test fired them in a .357 N-frame just in case. Average velocity was 787 with standard deviation of 28. A bit more smoke than usual and a higher SD then I like, but they were perfectly acceptable for casual use.
Your mileage may vary, of course.
edit: spelling