Maybe it has to do with ripening; here in a hot climate sweetness isn't the problem, usually it's blandly sweet. Developing good acid is the challenge to bring complexity to the fruit.

It could possibly be that the chill signals the onset of winter, which tells the fruit to get it in gear and finish ripening before the snow flies.

We've had a few frosts and last night it dropped to 24 F. Expect about the same tonight. The few Liberties I left on the tree are definitely better than the ones I picked a week ago, let along the two-week ago fruit.

Gold Spice pears picked as they began dropping and then left in the unheated garage have sweetened and tenderized.

I'm pretty encouraged with this year's results.