Central Oregon is blessed to have cool evenings and nights that produce prime baling weather. As the cool air settles down, condensation forms on the windows and help make a perfectly firm bale. However, it does take some planning ahead to have the moisture just right for the hay to not be too moist and cause mold problems in the stack.
I like to dry the hay out to 8% and then wait for the moisture to build to 11% or so before I start baling. This usually means I start baling at around 9 PM during first cutting and 7:30-8:00 during second cutting. If the hay is good and dry before the dew comes, the moisture is not in the stem and will dissipate through the bale and not cause any molding so the key is to get that windrow dry clear through before the dew hits. The dew helps the hay pack better and softens the hay to create more solid, heavier bales while lowering the dust contained in the bale.
I was baling alfalfa in Boardman, Or last year and we would start at 2 AM and barely got any dew because of the warm wind that constantly blows through the Columbia Basin. Tumalo, where I put up most of my hay, is at 3600 ft and we get lots of dew so we start earlier than most areas, the time that works best for you will be dependant on your location (in a valley, versus a hill), wind, and elevation.
If the hay is good and dry before the dew, I bale up to about 17% moisture before I quit for the night. I am pretty conservative, some guys go higher, but I don’t think its worth the mold potential. Once you can see moisture on your tires, start checking your meter frequently as the dew can set fast.