The winter problem can easily be solved with proper clothing. There are lightweight rain trousers you can wear above your normal clothes when it rains or snows, and of course a jacket with good ventilation.

The summers are more or less solved with e-bikes: you spend less energy paddling, while still profiting from airflow. I hear France has a subsidy for them. Unless you're in Spain or Southern Italy I guess, or there's a heatwave going on.

This is where picking a bike that suits your climate/circumstances come in.

I commute on a bike (at least, if I'm not going out after work) in London. I have a foldable Brompton bike fitted with an e-bike conversion kit from Swytch. I can ride in the middle of summer (ok, maybe not in those 40C days we just had) and arrive with no sweat. And if it rains, no matter, I stop, fold up my bike and jump on the Tube, or a bus.

but then your date is also sweaty, and both of you are in good shape!