Or does it make any difference whether fertilizer is applied right before or right after mowing?
Since you need to water it right away, probably better to do it after mowing.
Have you cooled off enough already to fertilize? Can you wait a few weeks?
It probably depends on what sort of grass you have.. and I forget what you have....
On my Bermuda -- I haven't noticed much difference unless I spill it so deep that it smothers the grass.... Then it turns brown for a day... and then it grows up over the house..
Do you bag or mulch your clippings? Probably not much difference, but, if you have a high-vac type mower and bagg, you might be sucking up some fertilizer that was just applied.
If you mulch, it might help get it further down by doing before, but, as Dchall mentions, you'd want to water right after if you use a chem fertilizer.
ooops, did I miss/forget something about not applying fertilizer in the heat?
I mulch mow, or I should say my lawn guy does. I just put down and watered in my second application of supergreen on my Bermuda only as this was recommended monthly through October as a way to choke out the crazy crabgrass invasion I am dealing with.
My prize lawn is the Turfallo patch which is doing great with no fertilizer or water from me. No crabgrass at all in the Turfallo! I think it may have to do with the fact that I prepped the area in March with cardboard and thick newspaper covered with top soil and mulch - must have prevented the crab seeds from germinating. Too bad I cant do that every year...I'd end up with a hill!