Mary Lake — Current Water Temperature, Annual Trends and Forecast
This page provides information on the current water temperature in Mary Lake, trends, monthly ranges and the forecast for the coming days.
Current Water Temperature
Water Temperature in Mary Lake today is 19.7°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 |
|---|---|---|---|
| AUG 24 | 20.5°C | 21.5°C | |
| AUG 25 | 20.3°C | 21.5°C | |
| AUG 26 | 19.8°C | 21.5°C | |
| AUG 27 | 21.0°C | 21.5°C | |
| AUG 28 | 20.7°C | 21.5°C | |
| AUG 29 | 20.8°C | 21.5°C | |
| AUG 30 | 20.4°C | 21.5°C | |
| AUG 31 | 19.7°C | 21.5°C | |
| SEP 1 | 19.5°C | 19.7°C | |
| SEP 2 | 19.5°C | 19.7°C | |
| SEP 3 | 19.5°C | 19.7°C | |
| SEP 4 | 19.5°C | 19.7°C | |
| SEP 5 | 19.5°C | 19.7°C | |
| SEP 6 | 19.5°C | 19.6°C | |
| SEP 7 | 19.5°C | 19.6°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 | 2°C | 4°C |
| February | 0°C | 2°C | 5°C |
| March | 0°C | 3°C | 6°C |
| April | 0°C | 6°C | 12°C |
| May | 4°C | 10°C | 16°C |
| June | 10°C | 15°C | 20°C |
| July | 16°C | 23°C | 29°C |
| August | 18°C | 22°C | 25°C |
| September | 17°C | 20°C | 22°C |
| October | 13°C | 16°C | 18°C |
| November | 3°C | 9°C | 14°C |
| December | 1°C | 4°C | 7°C |
Mary Lake: Water Temperature by Location
Mary Lake: Weather Forecast
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September 6
Location & Local Information
Mary Lake, part of a four-lake system near Huntsville in the Muskoka region of Ontario, experiences the typical seasonal temperature variations of a large inland lake. In the deep winter months, the lake freezes completely, with water temperatures near the freezing point, generally ranging from 0∘C to 5∘C (32∘F to 41∘F). During the peak summer season (July and August), the surface water warms considerably, typically reaching a comfortable range for swimming, likely peaking between 20∘C and 24∘C (68∘F to 75∘F).
Swimming is widely permitted and popular at Port Sydney Beach, which provides public access to Mary Lake's southwestern shore. This beach is a recognized swimming area and is routinely monitored for water quality by the Simcoe Muskoka District Health Unit during the summer for E. coli bacteria, confirming it as a designated recreational site. However, the beach is generally unsupervised, meaning there are no official lifeguards on duty, and all swimming is strictly at one's own risk. Swimmers should be mindful of boat traffic on the lake and adhere to any posted swimming advisories issued due to water quality concerns.