Everyone sweats when it is hot outside, but for some of them who have hyperhidrosis experience excessive sweating. Normally, while/after exercising, or during fever, nervousness or under stress the sweat glands produce perspiration that carries to the skin's surface. After these factors stop, the nerves that sends signal to perspire will be put on hold. Whereas, people having hyperhidrosis (like you) the sweat glands don't shut off, hence your hands keep sweating. Try using antiperspirant; it contains aluminium salts that works as a plug to perspiration. If the sweating still continues, then consult your doctor who can prescribe medication such as anticholinergic. As a precaution, there are some side effects such as palpitations, urinary infection etc. Best to talk to your doctor, and take his/her advise, if antiperspirants don't work.