Upper South Long Lake — Current Water Temperature, Annual Trends and Forecast
This page provides information on the current water temperature in Upper South Long Lake, trends, monthly ranges and the forecast for the coming days.
Current Water Temperature
Water Temperature in Upper South Long Lake today is 17.8°C.
Water Temperature: Daily Trends, Historical Records, and Forecast
⚠️ As of today, the minimum water temperature ranges from 60°F (15°C) to 65°F (18°C). The water is comfortable for most people, making it an ideal range for water sports enthusiasts. The temperature does not cause significant discomfort, and swimming will be pleasant for the majority. However, it's important to remember that prolonged exposure to the water can still lead to cooling, so it's essential to monitor the time spent in the water, especially for children or elderly people. 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 |
|---|---|---|---|
| SEP 14 | 20.9°C | 20.4°C | |
| SEP 15 | 19.6°C | 20.4°C | |
| SEP 16 | 19.7°C | 20.4°C | |
| SEP 17 | 17.7°C | 20.4°C | |
| SEP 18 | 17.9°C | 20.4°C | |
| SEP 19 | 18.0°C | 20.4°C | |
| SEP 20 | 18.0°C | 20.4°C | |
| SEP 21 | 17.8°C | 20.4°C | |
| SEP 22 | 20.4°C | 17.9°C | |
| SEP 23 | 20.4°C | 18.1°C | |
| SEP 24 | 20.4°C | 18.2°C | |
| SEP 25 | 20.4°C | 18.3°C | |
| SEP 26 | 20.4°C | 18.5°C | |
| SEP 27 | 20.4°C | 18.6°C | |
| SEP 28 | 20.4°C | 18.7°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 | 4°C |
| February | 0°C | 2°C | 4°C |
| March | 0°C | 2°C | 4°C |
| April | 2°C | 6°C | 10°C |
| May | 8°C | 15°C | 21°C |
| June | 15°C | 21°C | 27°C |
| July | 18°C | 23°C | 27°C |
| August | 20°C | 24°C | 28°C |
| September | 17°C | 20°C | 24°C |
| October | 6°C | 12°C | 18°C |
| November | 3°C | 7°C | 11°C |
| December | 1°C | 3°C | 6°C |
Upper South Long Lake: Water Temperature by Location
Upper South Long Lake: Weather Forecast
September 22
September 23
September 24
September 25
Location & Local Information
Upper South Long Lake in Minnesota follows the seasonal rhythm typical of shallow inland lakes in the region. In winter the surface is commonly at or below freezing, around 32°F (0°C) under ice cover, with water beneath the ice only slightly warmer. Spring thaw brings surface temperatures up into the 40–60°F range (4–15°C) as warming progresses, while summer is when the lake is warmest: surface readings often reach roughly 70–78°F (21–26°C), with shallow sheltered bays occasionally warming into the low 80s°F (27–28°C) on hot spells. Fall sees a steady decline back into the 50s–60s°F (10–15°C) range as cooling and turnover occur. Deeper parts of the lake remain cooler year-round.
Swimming is generally possible and commonly practiced in Upper South Long Lake during the ice-free months because summer and late-spring surface temperatures enter comfortable ranges for recreational bathing and there are public access areas that support swimming. However, access and swimming are subject to local rules, water-quality advisories, shoreline conditions and safety considerations; ice cover in winter makes open-water swimming unsafe except in controlled events with specialized precautions. It’s advisable to check current local advisories, watch for algal bloom notices in warm months, and use standard water-safety practices when entering the lake.