My first son was born on August 31. It was HOT. By the final weeks of my pregnancy, I was sausaged into enormous maternity sundresses that I'd once laughed at because sure, like that's EVER going to fit. Our house didn't have air conditioning and I had long surpassed that famed pregnancy "glow" for a pregnancy "all-out perspiration drench." The bones in my feet and ankles had disappeared entirely in favor of weird pillowy appendage-shapes that had the disturbing tendency to hold indentations if pressed with a morbidly curious finger.
In other words, being 80,000 months pregnant in the dog-days of summer sucked. If you'd asked me then, I would have claimed there was no way it could be less comfortable to have a baby during the dead of winter -- but then a few years later, I had my second son in February.
Now if you asked me which was worse, I'd say ... well, first I'd say what does it matter, when the joyous miracle of childbirth so thoroughly surpasses all creature comforts?