Flathead Lake — Current Water Temperature, Annual Trends and Forecast
This page provides information on the current water temperature in Flathead Lake, trends, monthly ranges and the forecast for the coming days.
Current Water Temperature
Water Temperature in Flathead Lake today is 23.2°C.
Water Temperature: Daily Trends, Historical Records, and Forecast
✅ As of today, the minimum water temperature ranges from 75°F (23°C) to 79°F (26°C). This is a very comfortable temperature for swimming, and many people can enjoy prolonged stays in the water without feeling cold. The water is pleasantly warm, making it ideal for relaxation and water sports. This temperature range is particularly popular among tourists, as it combines comfort and safety for health. 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 4 | 23.4°C | 21.5°C | |
| AUG 5 | 23.4°C | 21.5°C | |
| AUG 6 | 23.3°C | 21.5°C | |
| AUG 7 | 23.3°C | 21.5°C | |
| AUG 8 | 23.2°C | 21.5°C | |
| AUG 9 | 23.2°C | 21.5°C | |
| AUG 10 | 23.4°C | 21.5°C | |
| AUG 11 | 23.2°C | 21.5°C | |
| AUG 12 | 21.5°C | 23.1°C | |
| AUG 13 | 21.5°C | 23.0°C | |
| AUG 14 | 21.5°C | 22.9°C | |
| AUG 15 | 21.5°C | 22.9°C | |
| AUG 16 | 21.5°C | 22.8°C | |
| AUG 17 | 21.5°C | 22.7°C | |
| AUG 18 | 21.5°C | 22.6°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 | 1°C | 4°C |
| February | 0°C | 3°C | 5°C |
| March | 1°C | 3°C | 6°C |
| April | 1°C | 4°C | 8°C |
| May | 3°C | 9°C | 16°C |
| June | 11°C | 15°C | 18°C |
| July | 15°C | 19°C | 23°C |
| August | 18°C | 22°C | 25°C |
| September | 15°C | 18°C | 20°C |
| October | 8°C | 12°C | 16°C |
| November | 4°C | 6°C | 9°C |
| December | 0°C | 2°C | 5°C |
Flathead Lake: Water Temperature by Location
Flathead Lake: Weather Forecast
August 12
August 13
August 14
August 15
Location & Local Information
Flathead Lake is a large, relatively deep lake in northwest Montana, and its water temperatures reflect its alpine setting and seasonal weather. In spring the surface generally sits in the 40s to mid‑50s °F (about 4–13 °C) as snowmelt cools inflows. By early summer temperatures commonly reach the mid‑50s to mid‑60s °F (13–18 °C), and in July and August surface readings often warm into the 60s to low 70s °F (15–22 °C), with sheltered shallow bays occasionally climbing into the low‑ to mid‑70s °F (21–24 °C). As autumn arrives the lake cools back through the 50s and 40s °F (10–7 °C), and in winter surface temperatures approach freezing, roughly 33–40 °F (0.5–4 °C) in open water and colder where ice forms.
Swimming is permitted at public beaches and in many state and county parks around the lake, and people routinely swim in summer when surface temperatures are most comfortable. However, the water remains colder than many lowland lakes and can cause cold shock or hypothermia, especially outside peak summer months or in deeper water. Wind, sudden weather changes and limited lifeguard coverage at some sites mean swimmers should exercise caution, use flotation when appropriate, and be mindful of temperature and conditions before entering the water.