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LakeQuality

Updated July 2026

Portneuf River Warm Spring

Recorded at 93°F (34°C) in Idaho — classified Warm. Pleasantly warm and below typical hot-tub heat.
Recorded temperature
93°F / 34°C
Classification
Warm (86–99°F (30–37°C))
State
Idaho
Coordinates
42.7810, -111.9830

What this number is, and is not

93°F is the maximum surface temperature measured at the vent during the USGS/NOAA thermal springs survey (1965–1980). It is not a current reading, and the temperature of any pool downstream of a vent is almost always lower.

This page also records nothing about access. Land ownership, legal entry, trail conditions, and whether a usable pool exists are all outside this dataset. Confirm with the managing agency before setting out.

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Frequently Asked Questions

Portneuf River Warm Spring was recorded at 93°F (34°C), which classifies as Warm (86–99°F (30–37°C)). Pleasantly warm and below typical hot-tub heat. That figure is the maximum surface temperature measured at the vent during the USGS/NOAA survey between 1965–1980 — not a current reading, and not the temperature of any pool downstream of the vent.

This page classifies a temperature; it does not tell you whether a spring can be legally or safely reached. The inventory carries no information about land ownership, access, trail conditions, or whether a usable pool exists at all — many listed springs sit on private land or inside protected thermal areas where entry is prohibited. Confirm with the managing agency before setting out.

Portneuf River Warm Spring is in Idaho at approximately 42.7810, -111.9830. There is no LakeQuality-graded lake within 25 miles. Coordinates come from the USGS/NOAA inventory and locate the vent, not a trailhead or parking area.

All Idaho hot springs →Hot springs by state →Lake water temperature →

Source: USGS/NOAA Thermal Springs List for the United States, via PANGAEA (CC-BY-4.0). Compilation: USGS Waring 1965 / Muffler 1979 + NOAA NGDC KGRD-12 (1980).

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