Dee Why Lagoon – current water temperature and swimming conditions
This page provides information about the current water temperature at Dee Why Lagoon 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 Dee Why Lagoon today is 24°C.
Water Temperature in Dee Why Lagoon: Daily Trends, Historical Records, and Forecast
✅ Lake water between 20 and 25°C offers very comfortable swimming conditions for most people. Combined with warm air temperatures and calm weather, this range is ideal for extended swims and family activities. Because lakes lack strong currents, the water often feels gentler and warmer than rivers. Even with light cloud cover, swimming remains enjoyable.
Water Temperature Over the Last 30 Days
While water temperatures in Dee Why Lagoon declined overall during the past month, they have shown a noticeable rebound over the last week.
According to our forecast, the water temperature in Dee Why Lagoon will be 21.4°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 |
|---|---|---|---|
| Mar 12 | 24.0°C | 21.0°C | |
| Mar 13 | 24.0°C | 21.0°C | |
| Mar 14 | 22.3°C | 21.0°C | |
| Mar 15 | 22.1°C | 21.0°C | |
| Mar 16 | 22.1°C | 21.0°C | |
| Mar 17 | 22.1°C | 21.0°C | |
| Mar 18 | 24.0°C | 21.0°C | |
| Mar 19 | 24.0°C | 21.0°C | |
| Mar 20 | 24.0°C | 21.0°C | 24.0°C |
| Mar 21 | 21.0°C | 23.6°C | |
| Mar 22 | 21.0°C | 23.3°C | |
| Mar 23 | 21.0°C | 22.9°C | |
| Mar 24 | 21.0°C | 22.5°C | |
| Mar 25 | 21.0°C | 22.1°C | |
| Mar 26 | 21.0°C | 21.8°C | |
| Mar 27 | 21.0°C | 21.4°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
Dee Why Lagoon sits just behind the beach on Sydney’s Northern Beaches and is a shallow coastal lagoon influenced by rainfall, runoff, and seasonal weather rather than ocean conditions. Water temperature varies through the year but tends to be moderate. In summer, the lagoon usually warms to around 22–26°C, which can feel quite warm on still days. Spring and autumn typically sit between 18–22°C, while winter temperatures often drop to about 14–17°C. Because the lagoon is shallow, temperatures can change quickly depending on air temperature, sunshine, and recent rain.
Swimming Conditions
Swimming in Dee Why Lagoon is generally not recommended. While water temperatures in summer may appear suitable, water quality is often affected by urban runoff, stormwater inflow, and occasional algal growth, particularly after rain. For this reason, the lagoon is not managed as a designated swimming area, and locals usually avoid swimming there. After heavy rainfall, conditions can deteriorate further, with reduced clarity and increased health risks. As a result, most people choose the nearby ocean pool or beach for swimming instead. Overall, Dee Why Lagoon is best appreciated as a natural wetland and scenic feature rather than a recreational swimming spot, despite having seasonally mild water temperatures.