Being on a modern E-Bike in 39C is definitely way more comfortable than walking. You can adjust the power settings so you barely have to touch the pedals to move, it's less effort than walking, and you'll be traveling at up to 25 km/h so you'll get some air cooling you wouldn't get if you were just walking.
I've ridden mine in up to 35C and it's like stepping into an oasis compared to standing still in that temperature, more so if you wear clothing like loose fitting cotton clothing that benefits from the increased airflow.
>so you'll get some air cooling you wouldn't get if you were just walking.
39C is well above skin temperature so you're only going to get evaporative cooling and the effectiveness of that depends on humidity. It's possible the heating effect of the hot air blowing over your skin overwhelms the evaporative cooling and you are actually getting net warming.
Even if the humidity is low if you're not already drenched in sweet, it's going to feel awful.
In my experience this would be air heating and not air cooling because the air temperature is higher than the skin temperature, unless you're already sweating and being evaporatively cooled from that.
I've ridden mine in up to 35C and it's like stepping into an oasis compared to standing still in that temperature, more so if you wear clothing like loose fitting cotton clothing that benefits from the increased airflow.