Unnamed Thermal Spring

Napa County, California · Near Napa
38.3210°N, 122.2710°W · 600 ft
83°F 55°F air · Good soaking weather 600 ft Roadside Camping nearby (16.7 mi)

A warm spring with no name a couple of miles outside the city of Napa, right on Hagen Road. Its water on record is 83 degrees, lukewarm. It carries a USGS site number and has been photographed. Who owns the ground and if anyone may visit are both unrecorded, which matters this close to town.

Location
10 miles from American Canyon, CA

Fifty feet off Hagen Road, hardly a walk at all. Elevation is about six hundred feet. Snow does not occur, and the year brings about twenty-three inches of rain with a yearly average near sixty degrees. The record shows no land manager and no designation. OpenStreetMap contributes no second name, and there is no fee note.

The season on file is winter. The nearest campground listed is Oak Shores Day Use Area, about seventeen miles out, and by its name it may not allow overnight stays. The landowner is not on record, so confirm access before stopping. No fee or chemistry noted. Eighty-three degrees is warm to the hand and not much more.

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

A slice through the ground from west to east, about 0.6 miles end to end.

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

Heat Below
178 milliwatts per square meter of heat flow

That's about 2½ times the US average of 65. It's higher than at 98% 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
50°
Jan
52°
Feb
54°
Mar
59°
Apr
64°
May
70°
Jun
71°
Jul
71°
Aug
70°
Sep
66°
Oct
56°
Nov
50°
Dec
Annual Precip: 23.0 in Annual Snow: 0.0 in
Best Time to Visit
January Air 50°F · Water 83°F · +33° contrast
December Air 50°F · Water 83°F · +33° contrast
February Air 52°F · Water 83°F · +31° contrast
January offers 21°F more contrast than August
Current Conditions
55°F
Mostly Clear SSW 16.6 mph 94% Good soaking weather
Tuesday 79° Low 54° Areas Of Fog then Mostly Sunny
Spring is +4° warmer
Wednesday 73° Low 52° Patchy Fog then Partly Sunny 1% precip
Spring is +10° warmer
Thursday 77° Low 52° Areas Of Fog then Mostly Sunny
Spring is +6° warmer
Friday 82° Low 53° Areas Of Fog then Sunny
Spring is +1° warmer
Saturday 80° Low 53° Areas Of Fog then Mostly Sunny
Spring is +3° warmer
Where to Stay

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Nearby Camping
Oak Shores Day Use Area (Ca) 16.7 mi away

Overview Nestled between Blue Ridge and Cedar Roughs east of Napa Valley, Lake Berryessa provides ample public recreation opportunities. Popular activities on and around the large, yet uncrowded lake include fishing, boating, water skiing, wake boarding, jet skiing, sailing, swimming, kayaking, canoeing, wildlife viewing, hiking, biking and picnicking. The Dufer Point Visitor Center offers year-round interpretive events and exhibits highlighting natural and cultural resources. Lake Berrye...

Reservable Yes
Reserve on Recreation.gov →
Temperature
83°F
Warm Hot Boiling
Water Temp 83°F (28°C)
Avg Air Temp 61°F
Above Ambient +22°F
Warm air, warm water September
Access
Road Access Roadside
Nearest Road Hagen Road
Distance to Road 50 ft
Frequently Asked Questions
What is the water temperature at ?
has a water temperature of 83°F (28°C). This is a warm thermal spring.
Where is located?
is located in Napa County, California at 600 feet elevation, near Napa. Coordinates: 38.3210°N, 122.2710°W.
How do I get to ?
has Roadside road access, with the nearest road being Hagen Road (50 ft from the road).
Can I camp near ?
Yes, Oak Shores Day Use Area (Ca) is located nearby (16.7 miles away).
Sources: USGS NWIS