Lake Koocanusa — Current Water Temperature, Annual Trends and Forecast
This page provides information on the current water temperature in Lake Koocanusa, trends, monthly ranges and the forecast for the coming days.
Current Water Temperature
Water Temperature in Lake Koocanusa today is 17.2°C.
Water Temperature: Daily Trends, Historical Records, and Forecast
⚠️ As of today, the minimum water temperature ranges from 60°F (15°C) to 65°F (18°C). The water is comfortable for most people, making it an ideal range for water sports enthusiasts. The temperature does not cause significant discomfort, and swimming will be pleasant for the majority. However, it's important to remember that prolonged exposure to the water can still lead to cooling, so it's essential to monitor the time spent in the water, especially for children or elderly people. 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 | 19.6°C | 18.1°C | |
| SEP 15 | 19.4°C | 18.1°C | |
| SEP 16 | 19.1°C | 18.1°C | |
| SEP 17 | 18.3°C | 18.1°C | |
| SEP 18 | 17.7°C | 18.1°C | |
| SEP 19 | 17.4°C | 18.1°C | |
| SEP 20 | 17.7°C | 18.1°C | |
| SEP 21 | 17.2°C | 18.1°C | |
| SEP 22 | 18.1°C | 17.2°C | |
| SEP 23 | 18.1°C | 17.3°C | |
| SEP 24 | 18.1°C | 17.3°C | |
| SEP 25 | 18.1°C | 17.4°C | |
| SEP 26 | 18.1°C | 17.4°C | |
| SEP 27 | 18.1°C | 17.5°C | |
| SEP 28 | 18.1°C | 17.5°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 | 0°C | 3°C | 6°C |
| February | 0°C | 3°C | 5°C |
| March | 1°C | 3°C | 6°C |
| April | 1°C | 5°C | 9°C |
| May | 3°C | 10°C | 18°C |
| June | 12°C | 16°C | 19°C |
| July | 16°C | 20°C | 25°C |
| August | 19°C | 22°C | 25°C |
| September | 15°C | 18°C | 22°C |
| October | 8°C | 13°C | 17°C |
| November | 4°C | 6°C | 9°C |
| December | 0°C | 2°C | 5°C |
Lake Koocanusa: Water Temperature by Location
Lake Koocanusa: Weather Forecast
September 21
September 22
September 23
September 24
September 25
September 26
Location & Local Information
Lake Koocanusa, stretching across the border of northwestern Montana and southeastern British Columbia, is a long, narrow reservoir formed by the Libby Dam on the Kootenai River. Because it lies in a mountainous region, its water temperature varies significantly through the seasons. In early spring, the water remains very cold, averaging around 41–46°F (5–8°C) as snowmelt fills the reservoir. By late May and June, temperatures begin to rise to about 55–63°F (13–17°C), becoming more suitable for recreational activities. The warmest period occurs in July and August, when surface temperatures reach 68–73°F (20–23°C), particularly in the shallower bays and coves. As autumn approaches, cooling air and shorter days quickly lower the lake temperature to around 57°F (14°C) or less by October.
Swimming is allowed in Lake Koocanusa, and during midsummer it becomes quite popular among visitors and locals. The clear, clean water and scenic mountain backdrop make it an appealing location for swimming, boating, and paddleboarding. However, because much of the lake is deep and fed by cold mountain streams, the water can feel brisk even in July. The best swimming conditions occur between late June and early September, when the surface temperature is at its highest and the weather is consistently warm.