If hay is already cut but not raked a inch or two will not hurt it one bit.......after your down pour is over let top sun/wind dry then rake. you will never know that a drop fell on it, the key is that it was not raked into wind rows. we had to do it this year that way with the only rain we had during haymaking first cutting. My hay man has been at it for over 50 yrs and he calmed down my hysteria and he was 100% right. it is perfect, sweet smelling hay
Ruined no. How good it turns out depends on several factors. A drizzle is hardly ever a big deal but the drying conditions after the fact made a big difference IME. And I have drawer full of wet T-shirts. If the sun comes out soon after with good sunny temps, humidity in the 40s to low 50s and a nice breeze hay that has been rained on will still be pretty good, maybe on the brown side of green. I always wait for the top to dry out and tedd again. I have never dealt with hay up your way but around here, SE, PA this late in the season can be problematic especially if it is thick or has a lot of clover.
There are 2 schools of thought when rain comes into play. Some say rake so as to make a smaller “foot print” which makes sense if only a shower or drizzle is called for. IMO if it is going to be a soaker I don’t think it makes much difference. Though the ground around the wind rows will dry out faster before it is tedded again. However if the weather is not going to clear up straight away it is better in any case not to rake. Tight windrows create the perfect growing conditions for mold.