Lake Monona — Current Water Temperature, Annual Trends and Forecast
This page provides information on the current water temperature in Lake Monona, trends, monthly ranges and the forecast for the coming days.
Current Water Temperature
Water Temperature in Lake Monona today is 24.1°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 | 24.4°C | 22.5°C | |
| AUG 5 | 24.0°C | 22.5°C | |
| AUG 6 | 23.4°C | 22.5°C | |
| AUG 7 | 23.5°C | 22.5°C | |
| AUG 8 | 23.7°C | 22.5°C | |
| AUG 9 | 23.5°C | 22.5°C | |
| AUG 10 | 23.8°C | 22.5°C | |
| AUG 11 | 24.0°C | 22.5°C | |
| AUG 12 | 22.5°C | 24.0°C | |
| AUG 13 | 22.5°C | 23.9°C | |
| AUG 14 | 22.5°C | 23.9°C | |
| AUG 15 | 22.5°C | 23.8°C | |
| AUG 16 | 22.5°C | 23.7°C | |
| AUG 17 | 22.5°C | 23.6°C | |
| AUG 18 | 22.5°C | 23.5°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 | 2°C | 5°C |
| February | 1°C | 3°C | 6°C |
| March | 2°C | 5°C | 9°C |
| April | 4°C | 9°C | 14°C |
| May | 10°C | 14°C | 19°C |
| June | 15°C | 19°C | 23°C |
| July | 17°C | 24°C | 30°C |
| August | 18°C | 23°C | 27°C |
| September | 16°C | 19°C | 22°C |
| October | 9°C | 14°C | 19°C |
| November | 2°C | 6°C | 10°C |
| December | 0°C | 3°C | 6°C |
Lake Monona: Water Temperature by Location
Lake Monona: Weather Forecast
August 12
August 13
August 14
August 15
Location & Local Information
Lake Monona’s surface water temperature follows a clear seasonal pattern. After ice-out in spring, temperatures typically rise from roughly 40–60°F (4–15°C) as the lake mixes and warms. In summer the surface commonly sits between about 68–80°F (20–27°C), with occasional spikes into the low 80s–mid 80s°F (28–30°C) during heat waves. By early fall the water cools back into the 50s–60s°F (10–18°C) range before dropping toward freezing in winter; when the lake is iced over, surface temperatures are at or very near 32°F (0°C). Thermal stratification can occur in summer, so deeper water remains colder than surface readings.
Swimming in Lake Monona is allowed at municipal beaches and public access points during the warm months, and many residents and visitors swim there for recreation. Whether swimming is advisable depends on water-quality and safety conditions: local authorities post advisories for bacterial contamination or harmful blue‑green algal blooms that can arise in summer, and ice cover makes swimming unsafe in winter. Additional hazards include cold-water shock in shoulder seasons, boat traffic, and variable depths. People planning to swim should use designated swimming areas when available, heed posted warnings, and be aware of seasonal temperature changes that affect comfort and safety.