Ancell's Farmer is correct in the general case, but if you are intending to dig it into a bed that you won't be using until spring (the best part of six months away still! Help!), I can't see why not. The rain will dilute the as yet too concentrated nutrients. However, if it's got a lot of still unrotted straw or other bedding / litter (especially sawdust), I'd let it stand for longer, and preferably turn it to mix it up.