I was once walking around at 38°C degrees under the direct sun for three hours with zero sweating - not even a drop. It was dry air and pretty strong wind that removed all the sweat before it managed to collect on my skin. The indoor environment--no wind, high moisture and too high temperature--may make you sweat a lot.
Excessive sweating is when you sweat at rest, during the night or during mild exercise. Here's a list of
causes.