Savenac Cookhouse

Superior, Lolo National Forest, Montana

Tonight: low 39 °F, frost likely.

Tonight

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

Cold from below: pad

Your setup looks borderline for this night

You may feel chilly 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 outside39°F
  • Moisturefrost, keep your bag covered
  • Windcalm

Your night

  1. 10 p.m. to 3 a.m.ComfortableAir around you 53 to 42°F, heavy dew from 2 a.m.
  2. 3 a.m. until morningChilly. Add a layerAir around you 41 to 38°F, frost from 5 a.m.
Every hour
  • 10 p.m.52°Fcomfortable
  • 11 p.m.53°Fcomfortable
  • midnight52°Fcomfortable
  • 1 a.m.50°Fcomfortable
  • 2 a.m.42°Fcomfortable, heavy dew
  • 3 a.m.41°Fchilly, heavy dew
  • 4 a.m.40°Fchilly, heavy dew
  • 5 a.m.38°Fchilly, frost
  • 6 a.m.41°Fchilly
  • 7 a.m.41°Fchilly

This spot sits about 18 m below the land around it. On clear, calm nights cold air pools here, so expect it colder and wetter than the forecast.

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 35°F or colder

    Usually sold as a 26° 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.
  • Your spot sits lower than the ground around it. On a clear, calm night cold air drains into spots like this, so expect it colder and wetter than the forecast. If you can, move a little higher up, away from the creek or valley floor.
  • 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 (5 a.m.):

Outside at your spot
41°F
Warmth your shelter holds
+2 °F
Clear-sky cooling
−2 °F
Low spot
−4 °F
Air around you
37°F
Your bag's comfort rating
39°F
Cold ground through what you lie on
+4 °F
Your comfort limit
43°F

6 °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.

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