Unnamed Thermal Spring

San Bernardino County, California · Near Mentone
34.1240°N, 117.0780°W · 2,279 ft
90°F 59°F air · Good soaking weather 2,279 ft Open Short Walk US Forest Service Camping nearby (8.4 mi)

Nobody has named this thermal point, which sits on San Bernardino National Forest land five or so miles from Mentone. The water is warm, right at the edge of soaking temperature. It is not quite a mile from Santa Ana Truck Road, on Forest Service ground with open access. No name and no photo; the record is thin beyond the basics.

Location

Dry foothills at about 2,300 feet, with light snow. Santa Ana Truck Road is the nearest road, nine tenths of a mile away. National Forest land with no further designation. Green Valley campground is around eight miles off, the closest camp in the record.

December through February is what the record lists. A short walk off the truck road. Camp at Green Valley. No fee on file. The Forest Service has it as open. Temperature is on the low side of soakable, so on a cold morning it may feel cooler than you want.

Terrain

Aircraft with laser scanners measured this ground to within inches. The scan strips out trees and buildings, leaving the bare shape of the land around this spring.

Aerial view of the ground around the spring LiDAR bare-earth view of the same ground around the spring
Aerial LiDAR bare earth

Drag the handle to compare the two views. The orange dot marks the spring, in a frame about three quarters of a mile wide.

Setting
Canyon floor
Steep ground climbs away on both sides of the spring.
Highest ground nearby
797 ft above the spring
Within a quarter mile, to the southeast
Cross-section through the spring

A slice through the ground from northwest to southeast, about 0.6 miles end to end.

Elevation data: USGS 3D Elevation Program. Aerial imagery: USGS The National Map. Public domain.

Heat Below
106 milliwatts per square meter of heat flow

That's about 1½ times the US average of 65. It's higher than at 56% of the springs on this site.

Heat flow measures the warmth working its way up through the ground from deep inside the earth. Where it runs high, rain and snowmelt that seep down through cracks in the rock come back up hot.

Heat flow estimate: Stanford Thermal Earth Model (Aljubran & Horne, 2024), CC BY 4.0.

Monthly Climate
51°
Jan
52°
Feb
55°
Mar
60°
Apr
63°
May
73°
Jun
79°
Jul
80°
Aug
76°
Sep
67°
Oct
57°
Nov
50°
Dec
Annual Precip: 21.3 in Annual Snow: 3.9 in
Best Time to Visit
December Air 50°F · Water 90°F · +40° contrast
January Air 51°F · Water 90°F · +39° contrast
February Air 52°F · Water 90°F · +39° contrast
December offers 30°F more contrast than August
Current Conditions
59°F
E 10.8 mph 78% Good soaking weather
Today 84° Low 59° Sunny 2% precip
Spring is +6° warmer
Wednesday 81° Low 59° Sunny 1% precip
Spring is +9° warmer
Thursday 82° Low 60° Sunny
Spring is +8° warmer
Friday 85° Low 62° Sunny
Spring is +5° warmer
Saturday 87° Low 62° Sunny
Spring is +3° warmer
Where to Stay

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Nearby Camping
Green Valley 8.4 mi away

Overview Green Valley Campground is located near Arrowbear in the San Bernardino National Forest in Southern California. It is centered between Lake Arrowhead and Big Bear Lake, providing ample recreational opportunities in the area's pine-covered mountains. Green Valley Lake, known for its exceptional trout fishing, is located about a mile from this beautiful mountain campground.Recreation Green Valley Lake, which is known for its trout fishing, is located just minutes away. Boating and swim...

Reservable Yes
Reserve on Recreation.gov →
Temperature
90°F
Warm Hot Boiling
Water Temp 90°F (32°C)
Avg Air Temp 64°F
Above Ambient +26°F
Warm air, warm water September
Access
Open
Road Access Short Walk
Nearest Road Santa Ana Truck Road
Distance to Road 0.9 mi
Land
Ownership Federal
Agency US Forest Service
Designation National Forest
Unit San Bernardino National Forest
Manager US Forest Service
Protection 3 - Protected, subject to extractive use
Frequently Asked Questions
What is the water temperature at ?
has a water temperature of 90°F (32°C). This is a warm thermal spring.
Where is located?
is located in San Bernardino County, California at 2,279 feet elevation, near Mentone. Coordinates: 34.1240°N, 117.0780°W.
How do I get to ?
has Short Walk road access, with the nearest road being Santa Ana Truck Road (0.9 mi from the road).
Is free to visit?
has Open access. It is managed by US Forest Service.
Can I camp near ?
Yes, Green Valley is located nearby (8.4 miles away).