Covefix

When Is the First Freeze in Boise, ID?

NOAA 1991 to 2020 climate normals · station BOISE AIR TERMINAL

Typical first freezeOctober 21
Winterize byOctober 5
Last spring freezeApril 24

Quick Answer

The first freeze in Boise, ID typically arrives around October 21. There is a 10 percent chance it comes by October 5 and a 90 percent chance it has come by November 5. Finish winterizing outdoor faucets by October 5, and test the furnace by September 21. The average stretch between the last spring freeze and the first fall freeze is 179 days.

Your Boise winterizing calendar

Every date below is counted back from the earliest realistic freeze, October 5. Work through them in order and the pipes are safe even in an early year. If a date has already passed, do that step this weekend.

By September 7: clear the gutters and seal the gaps

Clean the gutters, caulk the window gaps, and replace a worn door sweep so heat stays in and ice doesn't build at the eaves.

By September 21: test the furnace and swap the filter

Run the heat for ten minutes on a mild day so a dead igniter or a tripped breaker shows up now, not on the first cold night. If it won't start, the furnace checklist covers the free fixes first.

By October 5: pull the hoses and drain the faucets

This is the date that matters. Unscrew every hose, close the indoor shutoff, drain each spigot, and cover it. The full routine is in how to winterize outdoor faucets.

After April 4: reverse it in spring

That is the date by which 90 percent of years have seen their last freeze. Open the indoor shutoff and check the wall behind each spigot for a split pipe before you trust it.

The numbers behind it

Chance a freeze (32°F or lower) has happened byFirst fall freezeLast spring freeze
10 percent (early year)October 5May 9
50 percent (typical year)October 21April 24
90 percent (late year)November 5April 4

Source: NOAA NCEI U.S. Climate Normals 1991 to 2020, station BOISE AIR TERMINAL (ID USW00024131, about 2,814 feet). The station is usually the airport, so a hilltop or a river valley across town can freeze a week earlier or later. See how Covefix uses this data.

FAQ

When is the first freeze in Boise, ID?

The typical first freeze in Boise, ID falls around October 21. There is a 10 percent chance it arrives by October 5 and a 90 percent chance it has arrived by November 5, based on NOAA 1991 to 2020 climate normals for the BOISE AIR TERMINAL station.

When should I winterize outdoor faucets in Boise?

Finish by October 5. That is the earliest date a freeze has even a 10 percent chance of having already happened in Boise, so disconnecting hoses, draining the spigots, and fitting covers before then protects the pipes in all but the earliest years.

When is the last frost in Boise, ID?

The typical last spring freeze in Boise, ID is around April 24. Wait until after April 4, the 90 percent date, before reversing winterizing steps like re-opening an outdoor shutoff.

Guides for this season

Outdoors & Seasonal

How to Clean Gutters Without Falling Off the Ladder

Clogged gutters dump water at your foundation. Here is the safe ladder setup, the scoop-and-flush method, and the downspout test most people skip.

Time2–4 hrs Cost$0–$60 moderate

Heating & Cooling

How to Replace an HVAC Filter the Right Way

A dirty HVAC filter cuts airflow and raises bills. Find the size, point the arrow toward the unit, and replace it in under 10 minutes today.

Time5–10 min Cost$8–$25 easy

Outdoors & Seasonal

Seal Drafty Windows Before the First Cold Snap

Find the leak with a smoking incense stick, then match the fix to the gap. And never caulk the weep holes at the bottom of a vinyl window frame.

Time30 min–2 hrs Cost$10–$45 easy

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