Island Park Reservoir — Current Water Temperature, Annual Trends and Forecast
This page provides information on the current water temperature in Island Park Reservoir, trends, monthly ranges and the forecast for the coming days.
Current Water Temperature
Water Temperature in Island Park Reservoir today is 20.9°C.
Water Temperature: Daily Trends, Historical Records, and Forecast
✅ As of today, the minimum water temperature ranges from 68°F (20°C) to 74°F (23°C). The water is warm and pleasant for swimming, and in this range, one can stay in the water for extended periods without the risk of hypothermia. This is the ideal temperature for relaxation, swimming, and water sports. Families with children, as well as outdoor enthusiasts, will enjoy swimming and time spent in the water. For most people, this is the optimal temperature for a comfortable beach experience. 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 |
|---|---|---|---|
| AUG 24 | 22.2°C | 23.0°C | |
| AUG 25 | 22.1°C | 23.0°C | |
| AUG 26 | 22.1°C | 23.0°C | |
| AUG 27 | 21.8°C | 23.0°C | |
| AUG 28 | 21.8°C | 23.0°C | |
| AUG 29 | 21.6°C | 23.0°C | |
| AUG 30 | 21.3°C | 23.0°C | |
| AUG 31 | 21.1°C | 23.0°C | |
| SEP 1 | 17.0°C | 20.7°C | |
| SEP 2 | 17.0°C | 20.5°C | |
| SEP 3 | 17.0°C | 20.3°C | |
| SEP 4 | 17.0°C | 20.1°C | |
| SEP 5 | 17.0°C | 19.9°C | |
| SEP 6 | 17.0°C | 19.7°C | |
| SEP 7 | 17.0°C | 19.5°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 | 5°C |
| February | 0°C | 3°C | 5°C |
| March | 1°C | 4°C | 6°C |
| April | 3°C | 6°C | 8°C |
| May | 4°C | 9°C | 14°C |
| June | 11°C | 14°C | 17°C |
| July | 13°C | 18°C | 23°C |
| August | 20°C | 23°C | 26°C |
| September | 14°C | 17°C | 20°C |
| October | 4°C | 9°C | 14°C |
| November | 0°C | 5°C | 9°C |
| December | 0°C | 3°C | 6°C |
Island Park Reservoir: Water Temperature by Location
Island Park Reservoir: Weather Forecast
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September 5
Location & Local Information
Island Park Reservoir, near Island Park, Idaho, is a relatively cool, high‑elevation body of water so temperatures tend to be lower than lowland lakes. Typical seasonal surface temperatures range from about 40–55°F (4–13°C) in late spring, warmest in midsummer around 60–70°F (15–21°C), and then falling to roughly 50–65°F (10–18°C) in early fall. In winter the surface can approach freezing, about 32°F (0°C) and below the ice the water remains just above freezing. These values vary with exact location in the reservoir, depth, wind, and seasonal weather patterns, so daily conditions can differ.
Swimming is generally allowed and commonly practiced during the warmer weeks of summer, but it is not a warm‑water swim venue; even peak summer temperatures are brisk compared with coastal or lowland lakes. Because the water is cool and can change quickly, swimmers should be prepared for cold shock and the risk of hypothermia, limit time in the water, and use flotation if not confident. Local regulations, posted advisories, boat traffic and entry points can affect safe access, so check current conditions and follow any management rules before swimming.