Mercer Spring
Mercer Spring is a tepid spring in the Coronado National Forest, Pima County, about five miles from Tanque Verde. The water is in the high seventies, cooler than a bath. Access is open on Forest Service land. Molino campground sits under a mile away. There is a picture on file and no chemistry, and there is a USGS entry for it.
A couple hundred yards off the North General Hitchcock Highway, which the record files under short walk. Forest Service ground, Coronado National Forest. It sits at a fair height, with a yearly average in the low sixties, a little snow some winters and fourteen inches of rain or thereabouts. Molino campground is the closest on file, less than a mile away.
The cold months are the ones on file as best, December through February. Park on the highway side and walk a couple hundred yards. Open access. Molino is the campground, close enough to walk. Nothing is written about fees. The water is cool, well under body heat, so there is no safety concern; the only question is if it feels warm enough to bother with on a given day.
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 Mercer Spring.
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
- 325 ft above the spring
- Within a quarter mile, to the south
A slice through the ground from south to north, about 0.6 miles end to end.
Elevation data: USGS 3D Elevation Program. Aerial imagery: USGS The National Map. Public domain.
That's close to the US average of 65. It's higher than at 14% 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.
See every spring on the geothermal heat map →
Heat flow estimate: Stanford Thermal Earth Model (Aljubran & Horne, 2024), CC BY 4.0.
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Overview Visitors are drawn to Molino Campground for its group camping area, scenic mountain surroundings and hiking and mountain biking opportunities. While most other campgrounds in the Catalina Mountains are closed in winter, Molino Campground and its picnic area are open in late fall, winter and early spring. The pleasant winter weather at this elevation makes it a great time to visit. Molino Basin is conveniently located 5.5 miles from the base of Mt. Lemmon on the Catalina Highway, and...
Mercer Spring is road-accessible, so you can bring more gear.
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