Manly Reservoir – current water temperature and swimming conditions
This page provides information about the current water temperature at Manly Reservoir in New South Wales. Here you can view recent temperature trends on a 30-day chart, check typical monthly water temperature ranges, and compare today’s reading with historical averages for this date. A 7-day water temperature forecast, local weather conditions, and an overview of swimming suitability are also included.
Current Water Temperature
The water temperature in Manly Reservoir today is 20°C.
Water Temperature in Manly Reservoir: Daily Trends, Historical Records, and Forecast
Water Temperature Over the Last 30 Days
While water temperatures in Manly Reservoir declined overall during the past month, they have shown a noticeable rebound over the last week.
According to our forecast, the water temperature in Manly Reservoir will be 18.0°C in the next 7 days. See the table below for daily data for the upcoming week.
Table of Daily Water Temperature Data
| Date | Current | Average | Forecast |
|---|---|---|---|
| Apr 8 | 19.6°C | 17.7°C | |
| Apr 9 | 18.8°C | 17.7°C | |
| Apr 10 | 18.8°C | 17.7°C | |
| Apr 11 | 18.8°C | 17.7°C | |
| Apr 12 | 20.0°C | 17.7°C | |
| Apr 13 | 20.0°C | 17.7°C | |
| Apr 14 | 18.1°C | 17.7°C | |
| Apr 15 | 18.1°C | 17.7°C | |
| Apr 16 | 20.0°C | 17.7°C | 20.0°C |
| Apr 17 | 17.7°C | 19.7°C | |
| Apr 18 | 17.7°C | 19.4°C | |
| Apr 19 | 17.7°C | 19.1°C | |
| Apr 20 | 17.7°C | 18.9°C | |
| Apr 21 | 17.7°C | 18.6°C | |
| Apr 22 | 17.7°C | 18.3°C | |
| Apr 23 | 17.7°C | 18.0°C |
* Current - Actual water temperature value
** Average - Average water temperature on this day in recent years
*** Forecast - Our water temperature forecast
Actual lake water temperatures may differ from the reported values by several degrees, particularly during periods of strong winds or rapid weather changes. Wind can mix surface and deeper layers in a lake, bringing cooler water to the surface, while shallow areas may warm more quickly under direct sunlight. Air temperature, sunshine, and cloud cover strongly influence how quickly a lake heats up or cools down. These factors can lead to noticeable temperature variations across different parts of the lake.
Our forecast is based on a proprietary mathematical model that considers real-time lake temperature observations, historical trends, seasonal cycles, wind strength and direction, and region-specific air temperature. To enhance accuracy, we also incorporate data from nearby monitored locations and comparable lakes within Australia.
Monthly Water Temperature Range (Min, Max & Average)
| Month | Today | Yesterday | A Week Ago |
|---|---|---|---|
| January | 15°C | 23°C | 26°C |
| February | 20°C | 23°C | 26°C |
| March | 19°C | 21°C | 24°C |
| April | 16°C | 18°C | 20°C |
| May | 11°C | 14°C | 17°C |
| June | 8°C | 11°C | 13°C |
| July | 8°C | 10°C | 13°C |
| August | 8°C | 11°C | 13°C |
| September | 12°C | 14°C | 17°C |
| October | 15°C | 17°C | 19°C |
| November | 18°C | 20°C | 24°C |
| December | 13°C | 23°C | 25°C |
Location & Local Information
Manly Reservoir sits just inland from the Northern Beaches and is surrounded by bushland, giving it a quiet, sheltered feel despite being close to suburban Sydney. Water temperature in the reservoir reflects the local coastal climate but remains relatively cool throughout the year. In summer, surface temperatures usually reach around 20–24°C, which can feel refreshing rather than warm, especially after cooler nights. Spring and autumn typically sit between 16–20°C, while winter sees temperatures drop to about 12–15°C. The depth of the reservoir means it warms and cools slowly, so sudden temperature changes are uncommon.
Swimming Conditions
Swimming in Manly Reservoir is not allowed. The lake is managed as part of Sydney’s drinking water supply system, and strict rules are in place to protect water quality. Activities involving direct contact with the water, including swimming, are prohibited regardless of season or temperature. Even in summer, when the water may appear suitable for a dip, access to the water is restricted and closely monitored. In addition, steep banks, variable depths, and limited safe entry points would make swimming unsafe even without the regulations. Overall, Manly Reservoir is best enjoyed for walking, cycling, and appreciating the surrounding bushland, with its water temperatures noted more out of interest than for recreation, as swimming is not permitted.