Grindstone Lake — Current Water Temperature, Annual Trends and Forecast
This page provides information on the current water temperature in Grindstone Lake, trends, monthly ranges and the forecast for the coming days.
Current Water Temperature
Water Temperature in Grindstone Lake today is 18.5°C.
Water Temperature: Daily Trends, Historical Records, and Forecast
⚠️ As of today, the minimum water temperature ranges from 65°F (18°C) to 68°F (20°C). This is already quite warm water, which is ideal for most people. Swimming becomes comfortable, and prolonged stays in the water do not cause discomfort. This temperature is perfect for family trips and for those who prefer warmer water. It is also comfortable for water sports such as surfing or swimming. 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 | 20.3°C | 20.6°C | |
| SEP 15 | 19.4°C | 20.6°C | |
| SEP 16 | 19.2°C | 20.6°C | |
| SEP 17 | 18.6°C | 20.6°C | |
| SEP 18 | 18.0°C | 20.6°C | |
| SEP 19 | 18.5°C | 20.6°C | |
| SEP 20 | 18.3°C | 20.6°C | |
| SEP 22 | 20.6°C | 18.6°C | |
| SEP 23 | 20.6°C | 18.7°C | |
| SEP 24 | 20.6°C | 18.8°C | |
| SEP 25 | 20.6°C | 18.9°C | |
| SEP 26 | 20.6°C | 19.0°C | |
| SEP 27 | 20.6°C | 19.1°C | |
| SEP 28 | 20.6°C | 19.2°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 | 7°C |
| February | 0°C | 4°C | 8°C |
| March | 0°C | 4°C | 8°C |
| April | 2°C | 8°C | 14°C |
| May | 8°C | 15°C | 20°C |
| June | 16°C | 22°C | 27°C |
| July | 19°C | 23°C | 28°C |
| August | 20°C | 24°C | 28°C |
| September | 18°C | 21°C | 23°C |
| October | 6°C | 13°C | 19°C |
| November | 3°C | 8°C | 12°C |
| December | 1°C | 4°C | 7°C |
Grindstone Lake: Water Temperature by Location
Grindstone Lake: Weather Forecast
September 22
September 23
September 24
September 25
Location & Local Information
Grindstone Lake in Minnesota follows the familiar seasonal pattern of northern lakes, with water temperatures that vary widely through the year. In summer, surface water commonly warms to roughly 65–78°F (18–26°C), especially in shallow bays and on hot, calm days. Spring brings a rapid transition from near-freezing after ice-out to roughly 40–60°F (4–16°C) as the season progresses. Autumn cools the surface back into the 45–65°F (7–18°C) range before freeze-up. During winter the lake is typically ice-covered and the water below the ice stays close to 32–39°F (0–4°C), with deeper layers remaining slightly warmer. Thermal stratification can develop in summer, so deeper water will be noticeably colder than surface readings.
Swimming at Grindstone Lake is generally possible and most common in the warm months when surface temperatures are in the comfortable summer range; public or private beaches and shorelines are used for recreation when conditions and water quality permit. Open‑water swimming is not advisable in spring or fall without precautions because of cold shock risk, and winter swimming is hazardous except for organized ice‑swim activities with proper safety measures. As with any lake, local rules, posted advisories, and personal preparedness (life jackets, awareness of currents and sudden temperature changes) should guide swimming decisions.