Long post - sorry - plenty of details.

I just noticed a problem with the recent drop in temperatures. I live in Northern VA at 1300 feet elevation. Normal temps are highs in low 40s and lows in mid 20Âs. But just recently, we had a big drop in temps with lows below 10 (this morning it was zero!) and highs in the 20Âs.

Issue is water dripping out of ceiling registers in 2 bedrooms on second story on opposite sides of the house. Only the registers close to the perimeter of the building and in the ceiling are dripping (interior ceiling registers in closets show no water). Some areas on floor are a few drops, one spot looked like a dog pee spot (but I did confirm it was not the dogs and was water from the vent). No wet drywall around registers  definitely looks like condensation coming out of the registers. Water is very cold. Windows have a lot of condensation on them at the bottoms of the glass.

I believe it is an issue with the humidifiers but I am not sure how to fix, or if I should touch them. In normal temps, they work fine with very little condensation on just one or 2 windows on rear of house that are in shade all year long. I have never seen water upstairs. But in past few days I have seen a lot of condensation buildup on all windows and glass patio doors on all levels of the house. The inside humidity is 44% in the master suite and 40% in the main living area, 46% in the second story bedrooms. Could the warm humid air from main level be rising and collecting in the second story ceiling registers? Why would water drip out of some registers but not others? What should I do to correct?

I just finished wiping up all the water and even though it is still very cold out (around 10 to 15 deg), the condensation seems to be drying up on many  but not all  of the windows. Those that are getting direct sun are dry, those in shade still have a little wetness but not much.

We live in a 2 story home (plus basement). Geothermal heating with Honeywell 225B bypass humidifiers on the 2 basement heat pumps (with Honeywell 1008 auto controllers with exterior thermometers hooked up to both units.) Main level has one 3 ton unit for 1500 sq ft master suite plus same size portion of basement below, and a 6 ton unit for 2400 sq feet living area on main floor plus same size portion of basement below (total of 7800 sq feet of total conditioned space between basement and main level). The second story is 1800 sq feet and has its own HVAC heat pump but no humidifier or dehumidifier. I have a whole house de-humidifier in the basement  set to keep humidity below 50% down there.

I normally do not run the second story HVAC (I have tstats set to 60) unless we have guests. Warm air rising from below keeps 2nd story rooms between 62 and 64 degrees, so second story heat pump almost never turns on. We keep the main floor tstats set to 65 and never change the settings. At begiining of winter I had previously adjusted the humidistat controllers per the directions. Could this condensation buildup just be due to the very fast drop in outside temps? Should I leave the settings alone, or adjust humidifier controllers again until water vapor disappears? It looks like relatively warmer air is on the way.

Thanks for the help.