Boulder Lake Reservoir — Current Water Temperature, Annual Trends and Forecast
This page provides information on the current water temperature in Boulder Lake Reservoir, trends, monthly ranges and the forecast for the coming days.
Current Water Temperature
Water Temperature in Boulder Lake Reservoir today is 21.6°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 | 22.0°C | 24.0°C | |
| AUG 25 | 21.8°C | 24.0°C | |
| AUG 26 | 21.3°C | 24.0°C | |
| AUG 27 | 21.1°C | 24.0°C | |
| AUG 28 | 21.3°C | 24.0°C | |
| AUG 29 | 21.5°C | 24.0°C | |
| AUG 30 | 21.5°C | 24.0°C | |
| AUG 31 | 21.5°C | 24.0°C | |
| SEP 1 | 16.1°C | 21.3°C | |
| SEP 2 | 16.1°C | 21.1°C | |
| SEP 3 | 16.1°C | 20.8°C | |
| SEP 4 | 16.1°C | 20.5°C | |
| SEP 5 | 16.1°C | 20.2°C | |
| SEP 6 | 16.1°C | 20.0°C | |
| SEP 7 | 16.1°C | 19.7°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 | 1°C | 3°C |
| February | 0°C | 1°C | 3°C |
| March | 0°C | 1°C | 3°C |
| April | 1°C | 5°C | 9°C |
| May | 2°C | 10°C | 17°C |
| June | 15°C | 18°C | 21°C |
| July | 18°C | 23°C | 27°C |
| August | 18°C | 24°C | 30°C |
| September | 14°C | 16°C | 19°C |
| October | 9°C | 13°C | 17°C |
| November | 1°C | 7°C | 11°C |
| December | 0°C | 2°C | 4°C |
Boulder Lake Reservoir: Water Temperature by Location
Boulder Lake Reservoir: Weather Forecast
September 1
September 2
September 3
September 4
September 5
September 6
Location & Local Information
Boulder Lake Reservoir in Minnesota typically follows seasonal temperature patterns common to small inland reservoirs. During summer, surface temperatures often range from about 60–78°F (16–26°C), with the warmest, shallow areas reaching the upper end of that span on hot, calm days. In spring and fall the surface commonly sits between roughly 40–60°F (4–16°C) as the water mixes and cools or warms, while in winter the water under ice hovers near freezing around 32°F (0°C). Depth, wind, and sunlight all influence local readings: shallow bays warm faster than deeper basins, and thermal stratification can leave bottom waters noticeably colder than surface values.
Swimming at Boulder Lake Reservoir is generally possible at public access points and shorelines unless signs or local regulations prohibit it; many reservoirs are multiuse for boating, fishing, and recreation. However, swimmers should be aware there are often no lifeguards, and water quality advisories, submerged hazards, aquatic vegetation, and cold-water shock in shoulder seasons can create risks. For safety, check posted rules and current conditions before entering the water, wear a life jacket when appropriate, and avoid swimming alone, especially when temperatures are cool or ice is present.