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 13°C.
Water Temperature in Dee Why Lagoon: Daily Trends, Historical Records, and Forecast
⚠️ Lake temperatures between 10 and 15°C are cold but can be manageable for short swims on sunny, warm days. Shallow areas may feel slightly warmer, while deeper sections remain cold and slow to warm up. Most swimmers keep sessions brief, and wetsuits are often used for comfort. Wind and cooler air temperatures can quickly reduce how pleasant the swim feels.
Water Temperature Over the Last 30 Days
Water temperatures in Dee Why Lagoonfell over the past month, but have levelled out during the last week.
According to our forecast, the water temperature in Dee Why Lagoon will be 11.3°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 |
|---|---|---|---|
| Jun 13 | 13.0°C | 11.0°C | |
| Jun 14 | 13.0°C | 11.0°C | |
| Jun 15 | 13.0°C | 11.0°C | |
| Jun 16 | 13.0°C | 11.0°C | |
| Jun 17 | 13.0°C | 11.0°C | |
| Jun 18 | 13.0°C | 11.0°C | |
| Jun 19 | 13.0°C | 11.0°C | |
| Jun 20 | 13.0°C | 11.0°C | |
| Jun 21 | 13.0°C | 11.0°C | 13.0°C |
| Jun 22 | 11.0°C | 12.8°C | |
| Jun 23 | 11.0°C | 12.5°C | |
| Jun 24 | 11.0°C | 12.3°C | |
| Jun 25 | 11.0°C | 12.0°C | |
| Jun 26 | 11.0°C | 11.8°C | |
| Jun 27 | 11.0°C | 11.5°C | |
| Jun 28 | 11.0°C | 11.3°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.