could be any number of things.
so first can we have some information before leaping to conclusions :-)

print temps , speeds, etc
Also is the extruder makign any extra noises ? Little clicks in particular.

Is it a new roll of filament ? is it a new brand ?
have you changed anything else ?

basically you cannot give too much information :-)

Off hand I can think of at leats three things it could be that have nothing to do with humidity or moisture - that's fairly rare and usually indicated by little 'popping' noises from the nozzle - or if you've been soaking it in a pond actual puffs of 'steam' - although that's pretty much only ever going to be cheap nylon.

So more info please :-)