Ask Dad

Depending on where you are you may be alright but not too short so you don’t stress the grass.

If you still have some good light and it’s not cold you can do the following

If less than 4” cut it down to 3” and you’re done.

More than 4”? Cut no more than 1/3 of it.

Give it a week or so and as long as there’s still some good light and it’s not too cold repeat.

You can read more here

https://www.homesandgardens.com/gardens/should-i-cut-my-grass-short-before-winter

Until that point, continue mowing once a week. Only once you’ve noticed your grass isn’t growing, or frost/snow covers your lawn, should you stop cutting it for winter. If the winter is particularly mild and the grass continues to grow, then carry on mowing occasionally throughout

Okay, so if you are putting a lawn mower away for the winter, you should check the oil, rebalance and sharpen the blade, and at least rinse off all the dead grass and dirt after the engine has cooled down.

I've done this.

Use the blower to move any piles of leaves. A few here and there aren't a problem, but if you can see the grass, you can't cut the grass.

Set the blade height as high as you can.

Overlap your lines more than normal to have the mower hit your clippings.

Run the blower again to distribute any clumps.

Wait a week and then do it one more time, even if the grass hasn't grown.

Better to do it on dry, sunny days, if you have the option.

I've used a push mower on long grass like this before. It's easier if you have an attachment to blow the cut grass out the side, otherwise (depending on moisture, especially under leaves) you'll likely get things clumping up pretty bad.