Henry's Fork Caldera

Crater Volcanic caldera forming Yellowstone hotspot's eastern volcanic complex

A volcanic caldera in eastern Idaho’s Island Park area, Henry’s Fork Caldera attracts geology enthusiasts and anglers who come for the Henry’s Fork River, fly-fishing and nearby geothermal features.

Main image

Henry’s Fork Caldera is a volcanic caldera in eastern Idaho associated with the Yellowstone hotspot track. It is a geologically significant feature within the northern Rocky Mountain volcanic province.

The caldera formed during a major volcanic event in the Pleistocene related to the Yellowstone hotspot; subsequent eruptions and tectonic activity have shaped the present landscape. It is one of several nested or adjacent calderas in the region created as the hotspot migrated.

The feature lies in eastern Idaho near Island Park and Henrys Lake, within a region of high plateaus and forested mountain terrain west of the Yellowstone Plateau.

  • Geologic context: Formed by volcanic activity associated with the Yellowstone hotspot, making it part of a chain of calderas across the northern Rocky Mountains.
  • Landscape: Surrounding terrain includes high plateau, lakes, and geothermal-influenced landscapes that attract geological and ecological study.
Henry's Fork Caldera
44.3069, -111.3893
Entrance to surrounding public lands generally free; commercial guided tours vary

How to Get to Henry's Fork Caldera #

The caldera is accessed via roads off Idaho highways serving the Island Park and Yellowstone regions. The nearest towns with services include Ashton and Island Park; many visitors arrive from West Yellowstone. Use US Forest Service maps and local guides for trailheads and backcountry planning.

Tips for Visiting Henry's Fork Caldera #

  • Visit early morning for geothermal steam and wildlife sightings.
  • Best visited with a map and local guidance if hiking - volcanic terrain can be disorienting.
  • Bring layers; high‑elevation mornings are cool even in summer.

Best Time to Visit Henry's Fork Caldera #

Late spring through early autumn is the best window for visiting the Henry's Fork Caldera and its high‑country features.

Summer
June-September · 5-25°C (varies with elevation)
Most accessible for hiking and observing caldera features.
Winter
December-March · -10-5°C
Snowbound and much less accessible; cross‑country skiing only for experienced parties.

Weather & Climate near Henry's Fork Caldera #

Climate

Henry's Fork Caldera's climate is classified as Warm-Summer Continental (Dry Summer) - Warm-Summer Continental (Dry Summer) climate with mild summers (peaking in July) and freezing winters (coldest in January). Temperatures range from -16°C to 26°C. Moderate rainfall (668 mm/year).

Temperature & Rainfall
Temperature Range
26°
Warmest Month
-16°
Coldest Month
Monthly Conditions

January

January is the coldest month with highs of -4°C and lows of -16°C. The wettest month with 85 mm of rain.

Comfort

-10°
Feels Like Freezing
-10°C
Temperature
-16° -4°

Weather

85 mm
Rainfall
3.1 m/s
Wind
Light Breeze

February

February is freezing with highs of 0°C and lows of -14°C. Moderate rainfall (65 mm).

Comfort

-7°
Feels Like Freezing
-7°C
Temperature
-14°

Weather

65 mm
Rainfall
3.1 m/s
Wind
Light Breeze

March

March is freezing with highs of 4°C and lows of -10°C. Moderate rainfall (60 mm).

Comfort

-3°
Feels Like Freezing
-3°C
Temperature
-10°

Weather

60 mm
Rainfall
3.5 m/s
Wind
Light Breeze

April

April is cold with highs of 9°C and lows of -5°C. Moderate rainfall (49 mm).

Comfort

Feels Like Cold
C
Temperature
-5°

Weather

49 mm
Rainfall
3.6 m/s
Wind
Light Breeze

May

May is cold with highs of 15°C and lows of 0°C. Moderate rainfall (60 mm).

Comfort

Feels Like Cold
C
Temperature
15°

Weather

60 mm
Rainfall
3.7 m/s
Wind
Light Breeze

June

June is cool with highs of 21°C and lows of 4°C. Moderate rainfall (56 mm).

Comfort

12°
Feels Like Cool
12°C
Temperature
21°

Weather

56 mm
Rainfall
3.5 m/s
Wind
Light Breeze

July

July is cool with highs of 26°C and lows of 6°C. Moderate rainfall (34 mm).

Comfort

16°
Feels Like Cool
16°C
Temperature
26°

Weather

34 mm
Rainfall
3.2 m/s
Wind
Light Breeze

August

August is cool with highs of 26°C and lows of 6°C. Moderate rainfall (35 mm).

Comfort

16°
Feels Like Cool
16°C
Temperature
26°

Weather

35 mm
Rainfall
3.1 m/s
Wind
Light Breeze

September

September is cool with highs of 21°C and lows of 1°C. Moderate rainfall (41 mm).

Comfort

11°
Feels Like Cool
11°C
Temperature
21°

Weather

41 mm
Rainfall
3.1 m/s
Wind
Light Breeze

October

October is cold with highs of 13°C and lows of -4°C. Moderate rainfall (41 mm).

Comfort

Feels Like Cold
C
Temperature
-4° 13°

Weather

41 mm
Rainfall
3.2 m/s
Wind
Light Breeze

November

November is freezing with highs of 3°C and lows of -9°C. Moderate rainfall (64 mm).

Comfort

-3°
Feels Like Freezing
-3°C
Temperature
-9°

Weather

64 mm
Rainfall
3.3 m/s
Wind
Light Breeze

December

December is freezing with highs of -3°C and lows of -15°C. Moderate rainfall (78 mm).

Comfort

-9°
Feels Like Freezing
-9°C
Temperature
-15° -3°

Weather

78 mm
Rainfall
3.1 m/s
Wind
Light Breeze

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