It's summer here. Even so, in the morning it's cold. When I get back is hot but I arrive at home and take a shower.

Then it depends on how you bike. Most people use a too low speed. This is like driving a car in first gear all the way to work. You will sweat. I use the highest gear comfortable. If it's too high my knees hurt.

Another thing is to find a slow constant rhythm. Do no "accelerate" on a bike. You will use a lot of energy and so you will sweat.