Not knowing your medical history makes it difficult to pinpoint potential of an underlying cause, so I'm going to throw possibilities at you and see if something sticks.
An area of red/hot skin is usually indicative of blood vessle/capilarie dialation in that area. When it is located on the hands, it is called Palmar Erythema and can happen for any number of reasons.
Most of the time, it is typically considered something you do not need to worry about if you are otherwise in good health.
Hormonal changes can have an influence on this. That said, taking birth control or hormone therapy can cause this. Also, if you are sexually active and are still able to become pregnant, this could be a potential cause.
This writer's best guess is, considering your age, Menopause or Premenopause is likely the best explaination.
Heredity can also play a role.
If you are still concerned after reading above, I would recommend talking with your primary healthcare provider about getting bloodwork to check for proper liver and thyroid function. Also get screened for Rheumatoid Arthritis and check for tumors.