Long Lake — Current Water Temperature, Annual Trends and Forecast
This page provides information on the current water temperature in Long Lake, trends, monthly ranges and the forecast for the coming days.
Current Water Temperature
Water Temperature in Long Lake today is 17.3°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 | 20.1°C | 21.2°C | |
| SEP 15 | 19.1°C | 21.2°C | |
| SEP 16 | 19.4°C | 21.2°C | |
| SEP 17 | 18.3°C | 21.2°C | |
| SEP 18 | 17.6°C | 21.2°C | |
| SEP 19 | 17.9°C | 21.2°C | |
| SEP 20 | 17.6°C | 21.2°C | |
| SEP 21 | 17.3°C | 21.2°C | |
| SEP 22 | 21.2°C | 17.5°C | |
| SEP 23 | 21.2°C | 17.7°C | |
| SEP 24 | 21.2°C | 17.9°C | |
| SEP 25 | 21.2°C | 18.1°C | |
| SEP 26 | 21.2°C | 18.3°C | |
| SEP 27 | 21.2°C | 18.5°C | |
| SEP 28 | 21.2°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 | 1°C | 7°C | 12°C |
| February | 1°C | 8°C | 15°C |
| March | 0°C | 9°C | 17°C |
| April | 3°C | 12°C | 20°C |
| May | 7°C | 14°C | 22°C |
| June | 15°C | 20°C | 24°C |
| July | 17°C | 22°C | 28°C |
| August | 20°C | 24°C | 28°C |
| September | 17°C | 21°C | 26°C |
| October | 5°C | 12°C | 18°C |
| November | 3°C | 7°C | 10°C |
| December | 1°C | 5°C | 8°C |
Long Lake: Water Temperature by Location
Long Lake: Weather Forecast
September 22
September 23
September 24
September 25
Location & Local Information
Long Lake in South Dakota typically follows the seasonal rhythm of prairie lakes. Surface waters are near freezing in winter, often around 32°F (0°C) under ice cover, while spring brings a steady rise into the 40–60°F (4–15°C) range as snowmelt and runoff cool the lake. In summer the surface commonly warms to roughly 70–80°F (21–27°C) and can reach the mid‑80s°F (about 29°C) during heat waves, especially in shallow bays. During autumn the lake cools again, with temperatures slipping back through the 50s–60s°F (10–15°C) as air temperatures drop and stratification breaks down.
Swimming is generally possible at Long Lake during the warmer months at public access points and designated beaches, but whether it is allowed at a specific location depends on local management and posted advisories. Cold water in spring and late fall increases the risk of cold‑water shock and hypothermia, and winter ice cover makes swimming unsafe. Episodes of harmful algal blooms, high bacteria counts after heavy rains, strong winds, or absence of lifeguards can lead officials to close beaches temporarily. For safety, check current local conditions and posted notices before entering the water.