Lake Sullivan — Current Water Temperature, Annual Trends and Forecast
This page provides information on the current water temperature in Lake Sullivan, trends, monthly ranges and the forecast for the coming days.
Current Water Temperature
Water Temperature in Lake Sullivan today is 18.6°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 |
|---|---|---|---|
| OCT 5 | 21.5°C | 20.0°C | |
| OCT 6 | 21.1°C | 20.0°C | |
| OCT 7 | 20.5°C | 20.0°C | |
| OCT 8 | 19.8°C | 20.0°C | |
| OCT 9 | 20.0°C | 20.0°C | |
| OCT 10 | 19.4°C | 20.0°C | |
| OCT 11 | 19.6°C | 20.0°C | |
| OCT 12 | 18.9°C | 20.0°C | |
| OCT 13 | 20.0°C | 18.7°C | |
| OCT 14 | 20.0°C | 18.7°C | |
| OCT 15 | 20.0°C | 18.8°C | |
| OCT 16 | 20.0°C | 18.9°C | |
| OCT 17 | 20.0°C | 19.0°C | |
| OCT 18 | 20.0°C | 19.0°C | |
| OCT 19 | 20.0°C | 19.1°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 | 7°C |
| February | 0°C | 4°C | 7°C |
| March | 1°C | 8°C | 15°C |
| April | 10°C | 14°C | 19°C |
| May | 15°C | 20°C | 24°C |
| June | 19°C | 23°C | 26°C |
| July | 23°C | 27°C | 31°C |
| August | 23°C | 27°C | 30°C |
| September | 21°C | 26°C | 31°C |
| October | 16°C | 20°C | 24°C |
| November | 8°C | 14°C | 20°C |
| December | 4°C | 8°C | 11°C |
Lake Sullivan: Water Temperature by Location
Lake Sullivan: Weather Forecast
October 13
October 14
October 15
October 16
October 17
October 18
Location & Local Information
Lake Sullivan’s surface water temperatures follow a typical Midwestern pattern, staying cold through late winter and spring and warming in summer. In winter the lake often hovers near freezing to the low 40s °F (about 1–5 °C). Spring brings a steady rise, with surface readings commonly in the mid 40s to mid 60s °F (7–18 °C) as air temperatures climb. By early to midsummer the lake usually warms into the 70s °F, roughly 21–27 °C, and peak summer surface temperatures can occasionally approach the upper 70s to low 80s °F (25–28 °C) on extended warm spells. Temperatures then decline through the fall back toward the 50s–60s °F (10–16 °C) before winter cooling resumes.
Swimming is typically done during the warmer months because the higher surface temperatures make recreational use comfortable; many visitors swim from shorelines, docks and public access points when conditions allow. Whether swimming is officially permitted at a particular spot depends on local rules and posted signage, and water quality advisories or boating traffic can affect safety. There may not be lifeguards at informal access areas, so swimmers should check current local guidance, observe posted regulations, and take standard precautions for water temperature, depth and currents before entering.