Warming up ones wet body near a fire:
Pouring cold water on one’s body and heating it near a fire : A person may not rinse his entire body in cold water and heat himself opposite a fire because by doing so he warms up the water that is on him and it is considered as if he has washed his entire body in hot water.
Pouring cold water on ones hot body: However one is allowed to rinse himself off with cold water after having heated up [his body] near a fire because the [cold] water that [will be poured] on him will not get so hot [to be considered that he has bathed in hot water].
Warming up ones wet hands: [Furthermore] there are opinions which say that even one who washes his hands needs to be careful not to heat it up opposite a fire even from an area where [the water on him will] not [reach] Yad Soledes, if one did not previously dry himself very well.
Their reasoning is: because by doing so he warms up the water that is on [his hands] and it is thus like he has bathed in hot water that was heated on Shabbos and hot water which was heated on Shabbos even in a permitted way is forbidden to wash even one limb and even if the [water] was only slightly heated that it is not Yad Soledes.
The Final Ruling: One is to be strict like this latter opinion.
One may not dry his hands near a source of heat as doing so heats up the water on his hands and transgresses the Bathing prohibition.