Rathbun Lake — Current Water Temperature, Annual Trends and Forecast
This page provides information on the current water temperature in Rathbun Lake, trends, monthly ranges and the forecast for the coming days.
Current Water Temperature
Water Temperature in Rathbun Lake today is 21.9°C.
Water Temperature: Daily Trends, Historical Records, and Forecast
✅ As of today, the minimum water temperature ranges from 68°F (20°C) to 74°F (23°C). The water is warm and pleasant for swimming, and in this range, one can stay in the water for extended periods without the risk of hypothermia. This is the ideal temperature for relaxation, swimming, and water sports. Families with children, as well as outdoor enthusiasts, will enjoy swimming and time spent in the water. For most people, this is the optimal temperature for a comfortable beach experience. 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 | 23.6°C | 23.3°C | |
| SEP 15 | 23.4°C | 23.3°C | |
| SEP 16 | 22.4°C | 23.3°C | |
| SEP 17 | 22.9°C | 23.3°C | |
| SEP 18 | 22.3°C | 23.3°C | |
| SEP 19 | 22.3°C | 23.3°C | |
| SEP 20 | 21.5°C | 23.3°C | |
| SEP 22 | 23.3°C | 22.0°C | |
| SEP 23 | 23.3°C | 22.0°C | |
| SEP 24 | 23.3°C | 22.1°C | |
| SEP 25 | 23.3°C | 22.2°C | |
| SEP 26 | 23.3°C | 22.3°C | |
| SEP 27 | 23.3°C | 22.3°C | |
| SEP 28 | 23.3°C | 22.4°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 | 4°C | 7°C |
| March | 2°C | 8°C | 14°C |
| April | 8°C | 13°C | 18°C |
| May | 13°C | 18°C | 23°C |
| June | 19°C | 22°C | 25°C |
| July | 24°C | 29°C | 32°C |
| August | 23°C | 26°C | 29°C |
| September | 21°C | 23°C | 26°C |
| October | 14°C | 18°C | 22°C |
| November | 4°C | 11°C | 16°C |
| December | 0°C | 2°C | 5°C |
Rathbun Lake: Water Temperature by Location
Rathbun Lake: Weather Forecast
September 22
September 23
September 24
September 25
Location & Local Information
Rathbun Lake, a reservoir in southern Iowa, undergoes clear seasonal shifts in surface temperature. In winter the surface can approach freezing, around 32–40°F (0–4°C). Spring sees a steady rise, with typical surface readings from roughly 45–65°F (7–18°C) by late spring. Summer is when the lake is warmest: surface temperatures commonly reach the mid-70s to low 80s°F, approximately 24–28°C, and on hot spells can climb a few degrees higher. In autumn the water cools again, moving from the 60s°F (15–20°C) in early fall down toward the 40s°F (4–9°C) as the season progresses. These figures vary with depth, wind, and weather patterns, so localized conditions can differ day to day.
Swimming at Rathbun is generally allowed at designated recreation areas and beaches managed around the reservoir, and the lake is commonly used for seasonal swimming when surface temperatures are most comfortable, typically late May through September. There are usually no lifeguards, so swimming is at visitors’ own risk, and authorities may post advisories for safety or water quality, including occasional blue‑green algae blooms. Bathers should check current conditions and posted notices before entering the water, and note that deeper or shaded areas remain considerably cooler than surface readings.