I go through this mental battle every fall. (our first frost is usually by mid October). I err on the side of waiting... it's not worth harvesting a crop if it's all un-ripe IMO. I harvested a week or two early one year, and didn't enjoy the quality of the high from slightly un-ripe buds. That being said, It really depends on the size of the grow, what the plants are being used for (some think getting high is all the same, and can't tell a difference in quality), and how many plants you have. I only grow a few plants, and I top them and train them a lot to keep them short and wide, so that I can build hoop houses over them and cover in the fall if needed. Right now I have a couple 7ft tall plants, and I was still able to hoop over them and throw plastic over to block the rain this week.

In past years though, I usually keep my plants under 5ft tall so that I can either drive stakes in to the ground and prop up plastic or blankets, or I use irrigation tubing to make hoop houses over them then cover for rain/frost. I think planning ahead of time is the key (all the way from the start), if you doing just a small personal grow.

I'll even risk a frost, and check the plants early in the am. If I see freeze damage, I'll chop. Obviously though, a large grow has different implications. It's emotionally tough every year though.

I put a fan on my outdoor if it gets cold enough to do damage

yes, stressful life of the farmer..

I've been in the same spot......at a certain time, the greenest plant in a field is a pot plant.....
Spot them from a mile away...