Aspen Grove Group Use Area (Helena-Lewis and Clark NF, MT)
Tonight: low 36 °F, frost likely, chance of rain, 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 52°F. The coldest are in February, when 1 night in 10 drops to -12°F. Frost is common in January, February, March, April, May, October, November and December.
- Jan18°F -3°FBag comfortable to 0°F · frost 99% · rain or snow 33% of days
- Feb15°F -12°FBag comfortable to -10°F · frost 97% · rain or snow 46% of days
- Mar22°F 8°FBag comfortable to 10°F · frost 95% · rain or snow 34% of days
- Apr27°F 14°FBag comfortable to 15°F · frost 76% · rain or snow 42% of days
- May35°F 28°FBag comfortable to 30°F · frost 30% · rain or snow 42% of days
- Jun44°F 37°FBag comfortable to 35°F · frost 0% · rain or snow 35% of days
- Jul52°F 46°FBag comfortable to 45°F · frost 0% · rain or snow 13% of days
- Aug51°F 45°FBag comfortable to 45°F · frost 0% · rain or snow 16% of days
- Sep44°F 36°FBag comfortable to 35°F · frost 5% · rain or snow 22% of days
- Oct34°F 19°FBag comfortable to 20°F · frost 43% · rain or snow 34% of days
- Nov (this month)24°F 7°FBag comfortable to 10°F · frost 80% · rain or snow 32% of days
- Dec19°F -1°FBag comfortable to 0°F · frost 96% · rain or snow 38% 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 lookMonday, November 9, 10 p.m. to 7 a.m.
Your setup looks borderline for this night
You may feel chilly from around 11 p.m.
Your spot sits in a hollow where cold air collects at night.
Best change
Move 20 to 50 meters higher, away from the valley floor or creek.
- On clear, calm nights it is often several degrees warmer there.
This is based on typical values for the gear types you picked, so treat it as an estimate.
Your night
- 10 p.m. to 11 p.m.ComfortableAir around you 43°F.
- 11 p.m. until morningChilly. Add a layerAir around you 43 to 35°F, frost, gusty from midnight, chance of rain from midnight (up to 31 mph).
Every hour
- 10 p.m.43°Fcomfortable
- 11 p.m.35°Fchilly, frost
- midnight40°Fchilly, gusty, chance of rain
- 1 a.m.40°Fchilly, some dew, gusty
- 2 a.m.42°Fchilly, gusty
- 3 a.m.42°Fchilly, gusty
- 4 a.m.43°Fchilly, some dew, gusty, chance of rain
- 5 a.m.42°Fchilly, some dew
- 6 a.m.41°Fchilly, some dew, gusty
- 7 a.m.41°Fchilly, some dew, gusty
This spot sits about 41 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-7).
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 11 p.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.
- Stake out every guyline and point the low, narrow end of the tent into the wind.
- Rain is possible from about midnight. Keep the rain fly on and bring shoes and packs inside.
- Bring shoes, clothes and electronics inside. Anything left out will be wet by morning.
How we estimated this
At the coldest hour (11 p.m.):
- Outside at your spot
- 37°F
- Warmth your shelter holds
- +5 °F
- Clear-sky cooling
- −1 °F
- Low spot
- −5 °F
- Air around you
- 36°F
- Your bag's comfort rating
- 39°F
- Cold ground through what you lie on
- +4 °F
- Your comfort limit
- 43°F
7 °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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