It could be due to a change in weather. Excessive sweating on palms is called palmar hyperhidrosis. It is usually also accompanied by excess sweating of feet. If it is sudden you could get your thyroid function tested. You will need to perform T3, T4, TSH. If normal there is nothing to worry about. The sweating increases when you are stressed, anxious and when the temperature is hot. Other factors like smoking, alcohol and spicy food also increase the sweating. You could use aluminium chloralhydrate solution available in a pharmacy with a dermatologist's prescription. It has to be applied daily night. Also there are other methods like iontophoresis, botulinum toxin and other medicines to reduce the sweating. I have written a detailed treatment option answer to a similar post a few days earlier. Warm regards. Dr. Rajdeep Mysore. Chirag Hospital Bangalore