A C25A Captain reported noticing a door seal warning light at FL450. He asked for lower and in the descent the light went out. After landing; a significant amount of water was purged from the seal.

Narrative

Cruising along at FL450; we heard a noise from the cabin. As I looked back; I did not see anything out of the ordinary. However; as I looked forward again; the MASTER CAUTION light illuminated as well as the 'DOOR SEAL' amber annunciator light. I donned my oxygen mask and told the ARTCC Controller that we needed lower. We were given FL410. I pulled out the checklist and we asked for and were eventually given a descent either all the way to or just towards FL310. In the descent; the lights extinguished and the sound stopped. We removed our masks and continued the flight to our destination. ATC did ask us what the problem was; but we did not declare an emergency or ask for priority handling. Our theory was that the door seal had accumulated moisture on the ground where it was hot; humid and we had the air conditioner running. At altitude; this water froze and prevented the door seal from inflating properly. At our destination; we purged the 23 PSI air line and lots of water was spit out.