September 25 is Boise’s average first frost. Will this year follow suit?

Tuesday is the day: Sept. 25 is the so-called average first frost, or the day when Boise has typically seen fall temperatures drop to 36 or below.

But that’s not going to happen this year — at least not at the Boise Airport, where the National Weather Service has kept records on first frost temperatures since 1877. Lows vary across the Treasure Valley, so you may well see frost on your pumpkins sooner.

The forecast low for Tuesday morning is 42, and low temperatures for the next week are expected to be in the 50s.

Four of the latest first frosts in Boise since they began keeping records were in the past seven years, according to Weather Service meteorologist Elizabeth Padian:

1. Nov. 16, 2016.

2. Nov. 3, 2015.

3. Oct. 27, 2014.

4. Oct. 25, 2011.

Boise’s average first freeze, or temperatures of 32 degrees or lower, is still about three weeks away: Oct. 11.

The lowest temperature we’ve seen so far this September was 44 degrees, according to National Weather Service climate data. That was on Sept. 18 and 20. First frost in Boise last year was Sept. 23.

Katy Moeller: 208-377-6413

This story was originally published September 24, 2018 at 7:16 PM with the headline "September 25 is Boise’s average first frost. Will this year follow suit?."