If I were to pressure wash my fence in mid-spring, could I leave it and not stain it until fall? The reason I ask is I have the time to wash the fence and my house, but I probably couldn't stain it for a few weeks, until it would be hot, and I'd rather wait until fall when it cools down a bit.
Some fences are never stained. Keep in mind that sunlight will "bleach" wood that is not protected from UV light. So, you can leave the fence as-is but it might significantly weather with no protection, depending on whether the pressure washing damages whatever existing finish is on it now.
Also, you don't necessarily want it to be hot when applying an exterior stain. Best time to stain would be a cloudy day. If the stain dries / cures too quickly it could lead to problems. Most exterior stains will instruct you to not expose the stained object to direct sun until the stain cures.