Nelson Reservoir — Current Water Temperature, Annual Trends and Forecast
This page provides information on the current water temperature in Nelson Reservoir, trends, monthly ranges and the forecast for the coming days.
Current Water Temperature
Water Temperature in Nelson Reservoir today is 11.8°C.
Water Temperature: Daily Trends, Historical Records, and Forecast
❌ As of today, the minimum water temperature ranges from 50°F (10°C) to 54°F (12°C). The water is slightly warmer, but still cool for most people. Swimming in such conditions is possible, but for most people, the time spent in the water should be limited to avoid hypothermia. Even experienced swimmers may feel discomfort if they stay in the water for too long. To improve comfort and safety, a wetsuit can be used. It is important to note that these swimming tips and recommendations apply only in good weather. When the air temperature is below 68°F (20°C), and sometimes even below 77°F (25°C), swimming can be unpleasant even with relatively high water temperatures.
Water Temperature Chart Over the Last 30 Days
Table of Daily Sea Temperature Data
| Date | Current | Average | Forecast |
|---|---|---|---|
| OCT 5 | 13.1°C | 11.0°C | |
| OCT 6 | 12.3°C | 11.0°C | |
| OCT 7 | 11.9°C | 11.0°C | |
| OCT 8 | 12.1°C | 11.0°C | |
| OCT 9 | 12.1°C | 11.0°C | |
| OCT 10 | 11.0°C | 11.0°C | |
| OCT 11 | 11.5°C | 11.0°C | |
| OCT 12 | 12.1°C | 11.0°C | |
| OCT 13 | 11.0°C | 11.8°C | |
| OCT 14 | 11.0°C | 11.7°C | |
| OCT 15 | 11.0°C | 11.7°C | |
| OCT 16 | 11.0°C | 11.6°C | |
| OCT 17 | 11.0°C | 11.6°C | |
| OCT 18 | 11.0°C | 11.6°C | |
| OCT 19 | 11.0°C | 11.5°C |
* Current - Actual water temperature value
** Average - Average water temperature on this day in recent years
*** Forecast - Our water temperature forecast
Actual nearshore water temperatures may fluctuate by several degrees from the reported values, especially following heavy rainfall or extended periods of strong winds. Certain wind patterns can cause colder, deeper waters to rise and replace the sun-warmed surface water, leading to noticeable variations.
Our forecast is based on a proprietary mathematical model that considers real-time water temperature changes, historical trends, key weather patterns, wind strength and direction, and air temperature specific to each region. Additionally, we incorporate data from other resorts to enhance accuracy.
Monthly Water Temperature Range (Min, Max & Average)
| Month | Min | Avg | Max |
|---|---|---|---|
| January | 0°C | 3°C | 6°C |
| February | 0°C | 4°C | 7°C |
| March | 0°C | 5°C | 9°C |
| April | 0°C | 6°C | 13°C |
| May | 4°C | 12°C | 21°C |
| June | 9°C | 15°C | 22°C |
| July | 16°C | 22°C | 28°C |
| August | 17°C | 22°C | 27°C |
| September | 13°C | 18°C | 23°C |
| October | 4°C | 11°C | 18°C |
| November | 4°C | 7°C | 10°C |
| December | 3°C | 7°C | 10°C |
Nelson Reservoir: Water Temperature by Location
Nelson Reservoir: Weather Forecast
October 13
October 14
October 15
October 16
October 17
Location & Local Information
Nelson Reservoir in Montana typically follows the seasonal temperature pattern common to inland reservoirs in the region. Surface water in summer often warms into the mid-60s to mid-70s °F (about 18–24 °C) during warm stretches, and late-summer sun can push localized surface spots slightly warmer. Spring and early summer are much cooler, with surface temperatures commonly ranging from the low 40s to low 60s °F (about 5–17 °C) as snowmelt and inflows keep the water cold. In the fall the water usually cools back into the 40s–50s °F (roughly 5–15 °C), and in winter the reservoir approaches freezing, with near-surface temperatures around 32 °F (0 °C) where ice forms.
Swimming at Nelson Reservoir is generally possible where public access and safe shore conditions exist, because reservoirs are commonly used for recreation. However, whether swimming is permitted at a particular access point depends on local rules, land ownership and current water-quality or safety advisories. Cold water, sudden temperature changes, boat traffic, undercurrents and lack of lifeguards are important considerations; many people restrict swimming to the warmest summer weeks and use flotation or supervision for safety. Checking local signage or land manager guidance before entering the water is recommended.