Lake Mary Ronan — Current Water Temperature, Annual Trends and Forecast
This page provides information on the current water temperature in Lake Mary Ronan, trends, monthly ranges and the forecast for the coming days.
Current Water Temperature
Water Temperature in Lake Mary Ronan today is 12.2°C.
Water Temperature: Daily Trends, Historical Records, and Forecast
⚠️ As of today, the minimum water temperature ranges from 54°F (12°C) to 60°F (15°C). The water is significantly warmer, and swimming becomes possible for most people. However, caution may still be required for prolonged stays in the water, as extended exposure can cause discomfort. This is a suitable temperature range for short swims and for those accustomed to cooler water. For more comfortable swimming, it is recommended to use proper gear. 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 | 13.9°C | 14.5°C | |
| JUN 4 | 13.8°C | 14.5°C | |
| JUN 5 | 13.7°C | 14.5°C | |
| JUN 6 | 13.7°C | 14.5°C | |
| JUN 7 | 14.0°C | 14.5°C | |
| JUN 8 | 14.1°C | 14.5°C | |
| JUN 11 | 14.5°C | 12.3°C | |
| JUN 12 | 14.5°C | 12.4°C | |
| JUN 13 | 14.5°C | 12.5°C | |
| JUN 14 | 14.5°C | 12.7°C | |
| JUN 15 | 14.5°C | 12.8°C | |
| JUN 16 | 14.5°C | 12.9°C | |
| JUN 17 | 14.5°C | 13.0°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 | 3°C | 5°C |
| March | 1°C | 3°C | 6°C |
| April | 1°C | 4°C | 7°C |
| May | 3°C | 9°C | 15°C |
| June | 11°C | 15°C | 18°C |
| July | 16°C | 19°C | 21°C |
| August | 18°C | 22°C | 25°C |
| September | 15°C | 18°C | 20°C |
| October | 8°C | 12°C | 16°C |
| November | 3°C | 6°C | 9°C |
| December | 0°C | 2°C | 5°C |
Lake Mary Ronan: Water Temperature by Location
Lake Mary Ronan: Weather Forecast
June 9
June 10
June 11
June 12
Location & Local Information
Lake Mary Ronan is a relatively cold, clear mountain lake in western Montana, so its water temperatures vary widely by season and depth. In spring (April–June) surface temperatures commonly range from about 45–60°F (7–16°C) as snowmelt and cool air keep the lake cold. By mid- to late summer (July–August) the surface can warm to roughly 60–72°F (15–22°C) on warm, sunny days, though deeper water remains much cooler—often in the 40s–50s°F (4–12°C) year-round. In fall the surface cools back toward 50–60°F (10–16°C) and the lake may freeze locally in winter when temperatures approach or drop below 32°F (0°C).
Swimming is permitted at Lake Mary Ronan because the shoreline includes public recreational areas and a state park that supports boating, fishing and beach access. However, the lake’s relatively low summer highs and cold subsurface temperatures mean swimmers should be prepared for brisk water and the risk of cold shock; buoyancy aids for weaker swimmers and caution around boats are recommended. Seasonal changes, weather and local rules can affect access and safety, so visitors typically check conditions at the park or with local officials before entering the water.