Little Bear Cabin

Bozeman, Custer Gallatin National Forest, Montana

Tonight: low 34 °F, frost likely, breezy.

Nights by month

Night lows from 2016 to 2025: a typical night, and the cold one that comes 1 night in 10.

The mildest nights are in July, typically 53°F. The coldest are in February, when 1 night in 10 drops to -2°F. Frost is common in January, February, March, April, May, October, November and December.

Typical nightCold night (1 in 10)
  1. Jan17°F 3°FBag comfortable to 5°F · frost 99% · rain or snow 37% of days
  2. Feb15°F -2°FBag comfortable to 0°F · frost 97% · rain or snow 49% of days
  3. Mar21°F 11°FBag comfortable to 10°F · frost 92% · rain or snow 47% of days
  4. Apr27°F 14°FBag comfortable to 15°F · frost 80% · rain or snow 51% of days
  5. May34°F 27°FBag comfortable to 25°F · frost 39% · rain or snow 57% of days
  6. Jun44°F 35°FBag comfortable to 35°F · frost 7% · rain or snow 54% of days
  7. Jul53°F 46°FBag comfortable to 45°F · frost 0% · rain or snow 37% of days
  8. Aug52°F 45°FBag comfortable to 45°F · frost 0% · rain or snow 32% of days
  9. Sep (this month)45°F 33°FBag comfortable to 35°F · frost 8% · rain or snow 34% of days
  10. Oct33°F 18°FBag comfortable to 20°F · frost 49% · rain or snow 40% of days
  11. Nov22°F 8°FBag comfortable to 10°F · frost 81% · rain or snow 37% of days
  12. Dec17°F 4°FBag comfortable to 5°F · frost 94% · rain or snow 39% of days

| = 32°F

History: ERA5 and ERA5-Land reanalysis via Open-Meteo, corrected to the site's elevation. Bag rating: the comfort rating that keeps you warm in a tent on 9 of 10 nights that month.

Tonight

Worth a lookFriday, September 25, 10 p.m. to 7 a.m.

Cold from below: pad

Your setup looks too cold for this night

Expected from around 3 a.m.

The cold comes from underneath: your pad does not insulate enough from the ground.

Best change

Add insulation underneath until you have about R2.5 in total (estimate).

  • A closed-cell foam mat under your pad adds about R2.
  • Folded blankets or spare clothes help if you have nothing else.

This is based on typical values for the gear types you picked, so treat it as an estimate.

  • Low outside34°F
  • Moisturefrost, keep your bag covered
  • Windgusty at times

Your night

  1. 10 p.m. to 3 a.m.ComfortableAir around you 61 to 42°F, heavy dew from 1 a.m., gusty (up to 33 mph).
  2. 3 a.m. to 6 a.m.Chilly. Add a layerAir around you 40 to 36°F, frost from 5 a.m.
  3. 6 a.m. to 7 a.m.Cold. Your setup is not warm enoughAir around you 35°F.
  4. 7 a.m. until morningChilly. Add a layerAir around you 38°F.
Every hour
  • 10 p.m.61°Fcomfortable, gusty
  • 11 p.m.51°Fcomfortable
  • midnight47°Fcomfortable, some dew
  • 1 a.m.44°Fcomfortable, heavy dew
  • 2 a.m.42°Fcomfortable, some dew
  • 3 a.m.40°Fchilly, heavy dew
  • 4 a.m.38°Fchilly, some dew
  • 5 a.m.36°Fchilly, frost
  • 6 a.m.35°Fcold
  • 7 a.m.38°Fchilly

Times are local time at your spot (GMT-6).

What works tonight

The gear this night calls for, for someone who sleeps like you.

  • Missing

    Sleeping bag

    Comfort 30°F or colder

    Usually sold as a 21° bag. The number in a bag's name is the limit, not the comfort.

  • Missing

    Underneath you

    R2.5 or more

    The R-value says how well a pad keeps the cold ground out.

  • Worth adding

    Also useful

    A bag liner

    Adds a few degrees to the bag you already own.

Before you sleep

  • Put on a warm layer and a hat before about 3 a.m., or go to bed already wearing them.
  • Eat a proper meal with some fat before bed. Your body keeps burning it through the night.
  • Pee right before you get in your bag. Getting out at 3 a.m. in the cold is worse.
  • Sleep in dry clothes, not the ones you wore all day. Damp fabric pulls heat out of you.
  • Fill a sturdy water bottle with hot (not boiling) water, check the lid does not leak, and put it in your bag by your core or feet.
  • Stake out every guyline and point the low, narrow end of the tent into the wind.
  • Bring shoes, clothes and electronics inside. Anything left out will be wet by morning.
  • Open the tent vents and keep the door zip open a bit at the top. Some condensation inside is normal on a night like this, so bring a small towel to wipe it off.
How we estimated this

At the coldest hour (6 a.m.):

Outside at your spot
34°F
Warmth your shelter holds
+2 °F
Clear-sky cooling
−2 °F
Air around you
34°F
Your bag's comfort rating
39°F
Cold ground through what you lie on
+4 °F
Your comfort limit
43°F

9 °F short, so you will likely be cold.

Assumptions

  • Bag categories use typical ratings as sold: summer about 50 °F (10 °C), 3-season about 30 °F (-1 °C), winter about 15 °F (-9 °C). The number in a bag's name is usually its lower limit, so its comfort rating is about 9 °F (5 °C) warmer.
  • What you lie on: foam mat about R2, thin air pad about R1.5, insulated pad about R3.5, winter pad R5 and up, van bed about R4, air mattress about R0.5. Colder ground needs a higher R-value.
  • Shelters hold a few degrees early in the night and less towards morning. Wind and clear, calm skies take warmth away.
  • Weather: Open-Meteo forecast for your spot, on a grid of a few kilometers, corrected to its height.
  • These are rules of thumb, not measurements. People and gear vary.

A forecast, not a promise. Mountains, valleys and water make their own weather, so trust what you see and feel on site. Terms and liability

Checked for a double-wall tent, a 3-season bag and a thin air pad. Check your own gear here.

Book or read more on Recreation.gov

Campgrounds nearby