B737-300
Flight Crew Air Transport Pilot (ATP)
Flight Crew Last 90 Days 134; Flight Crew Type 15000
Aircraft Equipment Problem Critical; Inflight Event / Encounter Weather / Turbulence
Flight Crew Overcame Equipment Problem; General Declared Emergency
Aircraft
We were enroute at FL 370. It was night/IMC with a significant area of thunderstorms along our route. The F/As were seated and the seatbelt sign was on due to potential turbulence. The First Officer was PF; and I was PM. We were in process of coordinating/accomplishing weather deviations when the Cabin Altitude Warning horn sounded. We immediately accomplished and verified the appropriate memory items; checked the cabin altitude (it was above 10;000'); and requested an immediate descent from ATC. A cursory check indicated that the air conditioning/pressurization systems were properly configured and no other warning lights were illuminated. We accomplished the Cabin Altitude Warning/Abnormal Pressurization Checklist; and since the cabin altitude was still uncontrollable (now at 12;000'); declared an emergency and requested descent to the highest of 10;000' or minimum vectoring altitude. I contacted the F/As; informed them of our pressurization situation; and advised them that the PSU oxygen masks might deploy. I asked them if there was any abnormalities in the cabin and was told outside of a squeaky door seal everything was normal. During our descent; we encountered constant moderate turbulence due to the convective activity in the area. We leveled off at 12;000'; at which point the pressurization was controllable. We were in constant moderate turbulence due to some low level cumulus clouds. We chose to climb back up to 16;000'; which was on top and the ride was smooth (the pressurization was stable).  We agreed to proceed to [destination] at 16;000' since the pressurization was now controllable. There was no evidence of any structural abnormality; [we] had sufficient fuel; and were past the convective activity. I contacted Dispatch and informed them of the situation and our plan to continue to [destination]. I made a PA giving our passengers an update on our pressurization situation; apologized for the bumpy ride; and updated ETA/weather. Outside of some minor sinus distress; all of the passengers were fine and no one needed any assistance.
B737-300 Captain reported loss of cabin pressure at FL370. Emergency was declared; the flight descended to 12;000 ft where pressurization control was regained.