I'd say trying to not die from heat exhaustion or stroke while riding uphill on a bike in 100+ degree weather is practical.
That's around 37 degrees celcius for us non-US people =).
I'm from Sydney, and we often have low 40's (Celcius) during summer. We currently have raging bushfires over here in some areas =(, and it's easily 40 degrees.
I bike to work (and also for fun on weekends) during that sort of temperatures, and I've never been worse for wear...
I also jog regularly during that weather (although I find that harder than biking - less breeze).
Mate - you're not going to get heat stroke from riding your bike a few Km at 37 degrees, seriously...
As your fitness improves, you'll probably find it easier.
Just stay hydrated (you do carry water, right?), apply sunscreen, and you'll be fine. Sure, it's harder work than driving a car, but exercise is hard work (despite what those late-night TV ads tell you).