Grass Lake — Current Water Temperature, Annual Trends and Forecast
This page provides information on the current water temperature in Grass Lake, trends, monthly ranges and the forecast for the coming days.
Current Water Temperature
Water Temperature in Grass Lake today is 20.3°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 |
|---|---|---|---|
| JUN 3 | 17.7°C | 18.0°C | |
| JUN 4 | 17.2°C | 18.0°C | |
| JUN 5 | 18.5°C | 18.0°C | |
| JUN 6 | 19.0°C | 18.0°C | |
| JUN 7 | 19.6°C | 18.0°C | |
| JUN 8 | 19.6°C | 18.0°C | |
| JUN 11 | 18.0°C | 20.2°C | |
| JUN 12 | 18.0°C | 20.1°C | |
| JUN 13 | 18.0°C | 20.0°C | |
| JUN 14 | 18.0°C | 19.8°C | |
| JUN 15 | 18.0°C | 19.7°C | |
| JUN 16 | 18.0°C | 19.6°C | |
| JUN 17 | 18.0°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 | 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 | 21°C |
| June | 14°C | 18°C | 22°C |
| July | 17°C | 21°C | 24°C |
| August | 20°C | 24°C | 28°C |
| September | 17°C | 20°C | 22°C |
| October | 5°C | 12°C | 18°C |
| November | 3°C | 7°C | 10°C |
| December | 1°C | 5°C | 8°C |
Grass Lake: Water Temperature by Location
Grass Lake: Weather Forecast
June 9
June 10
June 11
June 12
June 13
Location & Local Information
Grass Lake in eastern South Dakota follows the region’s seasonal pattern for surface water temperatures. In spring the lake typically runs cool as it thaws, roughly 40–60 °F (4–16 °C). By early summer surface temperatures often rise into the mid‑60s to upper‑70s °F (18–26 °C) on warm, calm days, with the warmest readings usually occurring in July and August. During autumn the water cools again, generally falling to the 50–65 °F range (10–18 °C) as air temperatures drop. In winter the lake freezes or hangs near 32 °F (0 °C) at the surface when ice is present; under‑ice temperatures remain close to 32 °F (0 °C) until spring thaw.
Swimming at Grass Lake is possible during the ice‑free months and is commonly done when water temperatures are comfortably warm, though actual access and permitted uses depend on local management and any posted advisories. Water quality, including occasional algae (blue‑green algae) blooms, can limit or discourage swimming for health reasons, and cooler waters below about 70 °F (21 °C) may feel uncomfortable without a wetsuit. Always check local signs or contacts for current water‑quality advisories, access rules, and safety information before entering the water, and avoid swimming when ice is present.