Unnamed Thermal Spring

Contra Costa County, California · Near Clayton
37.8950°N, 121.8740°W · 665 ft
70°F 84°F air 665 ft Open Roadside SPR
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.

Inside Mount Diablo State Park in Contra Costa County, roughly four miles from Clayton, there is an unnamed thermal point with water of about seventy degrees. Tepid. Nothing anyone would sit in, more a warm seep. The state park ground is listed as open, and the point sits a few dozen feet from a road, so reaching it takes little effort. A temperature is on record and little else.

Location

Low hills inside the state park at about 650 feet, no snow, dry apart from winter rain. Fifty-odd feet from the road edge. The California state park system manages the ground. No campground is recorded near this point in our data, and no fee is noted.

The listed window is midwinter, though the roads here stay clear year round. Roadside. State park rules apply. No fee recorded. No camping in the record for this point. The water is not warm enough for a meaningful soak, so come for the curiosity of it.

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.

Setting
Hillside
The spring sits on a steep slope that climbs to the northwest.
Highest ground nearby
276 ft above the spring
Within a quarter mile, to the northwest
Cross-section through the spring

A slice through the ground from southwest to northeast, about 0.6 miles end to end.

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

Heat Below
90 milliwatts per square meter of heat flow

That's about 1½ times the US average of 65. It's higher than at 30% 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
48°
Jan
50°
Feb
53°
Mar
57°
Apr
61°
May
67°
Jun
70°
Jul
70°
Aug
68°
Sep
64°
Oct
54°
Nov
48°
Dec
Annual Precip: 16.5 in Annual Snow: 0.1 in
Best Time to Visit
January Air 48°F · Water 70°F · +22° contrast
December Air 48°F · Water 70°F · +22° contrast
February Air 50°F · Water 70°F · +20° contrast
January offers 22°F more contrast than July
Current Conditions
84°F
S 32.4 mph 21%
Tuesday 84° Low 56° Sunny
Wednesday 76° Low 56° Sunny 1% precip
Thursday 82° Low 56° Sunny
Friday 86° Low 57° Sunny
Saturday 83° Low 58° Sunny 1% precip
Temperature
70°F
Warm Hot Boiling
Water Temp 70°F (21°C)
Avg Air Temp 59°F
Above Ambient +11°F
Mild soaking conditions September
Access
Open
Road Access Roadside
Distance to Road 57 ft
Land
Ownership State
Agency SPR
Designation State Park
Unit Mount Diablo State Park
Manager SPR
Protection 4 - No known protection
Frequently Asked Questions
What is the water temperature at ?
has a water temperature of 70°F (21°C). This is a warm thermal spring.
Where is located?
is located in Contra Costa County, California at 665 feet elevation, near Clayton. Coordinates: 37.8950°N, 121.8740°W.
How do I get to ?
has Roadside road access (57 ft from the road).
Is free to visit?
has Open access. It is managed by SPR.