Sullivan Lake — Current Water Temperature, Annual Trends and Forecast
This page provides information on the current water temperature in Sullivan Lake, trends, monthly ranges and the forecast for the coming days.
Current Water Temperature
Water Temperature in Sullivan Lake today is 14.8°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 |
|---|---|---|---|
| SEP 14 | 17.8°C | 18.1°C | |
| SEP 15 | 16.7°C | 18.1°C | |
| SEP 16 | 16.4°C | 18.1°C | |
| SEP 17 | 15.8°C | 18.1°C | |
| SEP 18 | 15.9°C | 18.1°C | |
| SEP 19 | 15.1°C | 18.1°C | |
| SEP 20 | 14.6°C | 18.1°C | |
| SEP 21 | 14.8°C | 18.1°C | |
| SEP 22 | 18.1°C | 15.0°C | |
| SEP 23 | 18.1°C | 15.1°C | |
| SEP 24 | 18.1°C | 15.3°C | |
| SEP 25 | 18.1°C | 15.5°C | |
| SEP 26 | 18.1°C | 15.6°C | |
| SEP 27 | 18.1°C | 15.8°C | |
| SEP 28 | 18.1°C | 16.0°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 | 3°C | 5°C |
| February | 1°C | 3°C | 6°C |
| March | 1°C | 4°C | 7°C |
| April | 0°C | 4°C | 9°C |
| May | 4°C | 9°C | 15°C |
| June | 9°C | 13°C | 17°C |
| July | 14°C | 19°C | 24°C |
| August | 18°C | 21°C | 24°C |
| September | 14°C | 18°C | 23°C |
| October | 9°C | 13°C | 16°C |
| November | 5°C | 8°C | 11°C |
| December | 1°C | 4°C | 7°C |
Sullivan Lake: Water Temperature by Location
Sullivan Lake: Weather Forecast
September 22
September 23
September 24
September 25
September 26
Location & Local Information
Sullivan Lake in Washington typically shows the temperature patterns of small inland lakes in the region: water remains quite cool through spring, warms modestly in summer, and cools again in fall and winter. Typical seasonal surface temperature ranges are roughly 34–55°F (1–13°C) in spring, 60–72°F (15–22°C) in summer at the warmest, 45–60°F (7–16°C) in early fall, and near freezing to about 40°F (0–4°C) in winter. Actual temperatures depend on recent weather, lake depth, inflow from creeks or springs, and elevation; deeper layers remain colder year-round, and shallow bays warm fastest on sunny days.
Swimming is generally allowed at Sullivan Lake as it is used for recreation, but there are no guarantees of lifeguards or facilities, so swimmers should follow posted rules and local guidance. Cold water, sudden temperature gradients, and underwater hazards make caution important even in summer when surface temperatures are highest. Boat traffic, watercraft, and occasional poor water quality or algal advisories can further limit safe swimming; checking current conditions and wearing a personal flotation device when appropriate improves safety.