Is this a valid reason to cancel a doctors appointment?

Tomorrow I have an appointment with a ~1 hr commute on public transit. I will need to walk ~15minutes once in the area, to reach the practice.

I checked the weather for the area, and the time I will be there, it will be at ~70% humidity, and feel like 99 degrees Fahrenheit.

I feel guilty for wanting to reschedule. I would need contact my ride (to public transit) last minute and ask if they're available another day.

Around a week ago I had this appointment in place, but had transportation issues and called them while on the way, that I wouldn't make it in time.
So, rescheduling this would be my third attempt.
I recently got the doctor to approve a refill, because he knew I had rescheduled, and he'd be able to see me . But now I'm pushing it back again!!

I'm very anxious about this. What would you do? I have the medication now, so I'm not worked up/motivated by needing to go, so it'd be refilled, now. I'm overthinking but I'm so anxious about it.