Where I am near the Puget Sound, I generally get around 50-60% relative humidity at outside temperatures. Which isn't really very humid. But my basement sits at 5-10 degrees cooler than outside temperature, and the same water content in the air, but 5-10 degrees cooler is a recipie for puddles in the basement. Running the ground floor A/C makes it worse, as the air handler is in the basement and cools the utility room through convection of the vents (better design of HVAC would help, but it'd hard to retrofit without tearing up a lot of stuff). Running a dehumidifier helps, but a more efficient dehumidifier might be nice.