I knew something was wrong when I came home and all my windows were fogged up. I do live in Alabama- it's been raining all day and is 41. When the gas central heat comes on it's like a sauna! What's going on?

Do you have a carbon monoxide detector? One possible problem is that somehow combustion products from the furnace are making it into the house. That is a serious problem. If you have a working CO monitor, and it hasn't gone off, likely that is not the problem. That is the purpose of the detector, to alert you to such a problem when it happens.

If the moisture is from the combustion, you need to check both the vent and the heat exchanger of the furnace. The air that circulates through the house is separated from the air that goes in the combustion chamber by the heat exchanger. One goes to your ducts, and the other up the chimney. If you don't feel confident about checking the heat exchanger and vent, call a professional.

On the other hand you have a CO detector quietly hanging on the wall wit fresh batteries, look elsewhere for the problem. Maybe up in the attic. Rain could be working its way in somewhere and raising the humidity even more than what comes in with the air. Next, try the basement or crawl space. Most attics and crawl spaces have plenty of leaks into the living space to all cold air and moisture in. Your hot water heater could have even decided to let off a little steam. Look for a puddle below the relief valve.

How long have you been in the house? Did you have less moisture on a day like today in the past? Do a little checking, and get back with me. This may or may not be something you can find and fix yourself. No reason to panic if you are reasonably handy.

Thanks for your reply- we had a lot of rain and where my furnace is located got @ 15inches of water. Sump pump got that out- now I don't know if I should let my unit run or call for service. If it's something simple I'd like to check it myself. I did turn on the unit yesterday and it was still blowing out warm, very moist air. Had to turn off using breaker- it won't turn off w/just the thermostate.