Lava Flow Campground

Arco, Craters Of The Moon National Monument & Preserve, Idaho

Tonight: low 46 °F, calm and dry.

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 56°F. The coldest are in February, when 1 night in 10 drops to 1°F. Frost is common in January, February, March, April, May, October, November and December.

Typical nightCold night (1 in 10)
  1. Jan13°F 2°FBag comfortable to 5°F · frost 100% · rain or snow 31% of days
  2. Feb13°F 1°FBag comfortable to 0°F · frost 100% · rain or snow 33% of days
  3. Mar19°F 8°FBag comfortable to 10°F · frost 96% · rain or snow 32% of days
  4. Apr25°F 13°FBag comfortable to 15°F · frost 88% · rain or snow 32% of days
  5. May34°F 25°FBag comfortable to 25°F · frost 41% · rain or snow 41% of days
  6. Jun45°F 33°FBag comfortable to 35°F · frost 6% · rain or snow 26% of days
  7. Jul56°F 48°FBag comfortable to 50°F · frost 0% · rain or snow 12% of days
  8. Aug54°F 46°FBag comfortable to 45°F · frost 0% · rain or snow 17% of days
  9. Sep (this month)45°F 35°FBag comfortable to 35°F · frost 5% · rain or snow 19% of days
  10. Oct32°F 20°FBag comfortable to 20°F · frost 50% · rain or snow 23% of days
  11. Nov22°F 10°FBag comfortable to 10°F · frost 89% · rain or snow 26% of days
  12. Dec14°F 0°FBag comfortable to 0°F · frost 98% · rain or snow 29% 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

Good nightFriday, September 25, 10 p.m. to 7 a.m.

Warm enough at the coldest hour

Your selected gear looks warm enough

About 8 °F to spare at the coldest hour.

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

  • Low outside46°F
  • Moisturedry
  • Windcalm

Your night

  1. 10 p.m. until morningComfortableAir around you 61 to 47°F.
Every hour
  • 10 p.m.61°Fcomfortable
  • 11 p.m.58°Fcomfortable
  • midnight55°Fcomfortable
  • 1 a.m.53°Fcomfortable
  • 2 a.m.51°Fcomfortable
  • 3 a.m.50°Fcomfortable
  • 4 a.m.48°Fcomfortable
  • 5 a.m.48°Fcomfortable
  • 6 a.m.47°Fcomfortable
  • 7 a.m.47°Fcomfortable

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

What works tonight

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

  • You have this

    Sleeping bag

    Comfort 45°F or colder

    Usually sold as a 36° bag. The number in a bag's name is the limit, not the comfort.

  • You have this

    Underneath you

    R1.5 or more

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

How we estimated this

At the coldest hour (7 a.m.):

Outside at your spot
46°F
Warmth your shelter holds
+2 °F
Clear-sky cooling
−1 °F
Air around you
47°F
Your bag's comfort rating
39°F
Your comfort limit
39°F

8 °F to spare, so warm enough.

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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