Cosseys Reservoir – current water temperature and swimming conditions
This page provides information about the current water temperature at Cosseys Reservoir in Auckland Region. 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 Cosseys Reservoir today is 11°C.
Water Temperature in Cosseys Reservoir: 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 Cosseys Reservoir have been gradually cooling over the past month, with a further drop recorded during the last week.
According to our forecast, the water temperature in Cosseys Reservoir will be 12.6°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 |
|---|---|---|---|
| Aug 19 | 15.3°C | 12.9°C | |
| Aug 20 | 14.9°C | 12.9°C | |
| Aug 21 | 14.7°C | 12.9°C | |
| Aug 22 | 14.7°C | 12.9°C | |
| Aug 23 | 14.7°C | 12.9°C | |
| Aug 24 | 14.9°C | 12.9°C | |
| Aug 25 | 10.8°C | 12.9°C | |
| Aug 26 | 10.8°C | 12.9°C | |
| Aug 27 | 10.8°C | 12.9°C | 10.8°C |
| Aug 28 | 12.9°C | 11.1°C | |
| Aug 29 | 12.9°C | 11.3°C | |
| Aug 30 | 12.9°C | 11.6°C | |
| Aug 31 | 12.9°C | 11.9°C | |
| Sep 1 | 12.9°C | 12.1°C | |
| Sep 2 | 12.9°C | 12.4°C | |
| Sep 3 | 12.9°C | 12.6°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 New Zealand.
Monthly Water Temperature Range (Min, Max & Average)
| Month | Today | Yesterday | A Week Ago |
|---|---|---|---|
| January | 19°C | 22°C | 25°C |
| February | 17°C | 21°C | 25°C |
| March | 16°C | 20°C | 24°C |
| April | 14°C | 17°C | 20°C |
| May | 12°C | 15°C | 17°C |
| June | 9°C | 13°C | 16°C |
| July | 7°C | 11°C | 14°C |
| August | 9°C | 12°C | 14°C |
| September | 10°C | 13°C | 16°C |
| October | 11°C | 15°C | 19°C |
| November | 15°C | 18°C | 21°C |
| December | 16°C | 19°C | 22°C |
Cosseys Reservoir: Weather Forecast
August 28
August 29
August 30
August 31
September 1
Location & Local Information
Cosseys Reservoir, in the Auckland Region near Hunua, is a water supply reservoir set within the Hunua Ranges Regional Park. Surrounded by native bush and managed primarily for drinking water, its water temperature follows seasonal air conditions typical of the upper North Island. In winter, surface temperatures are generally around 11–15°C. During spring, the reservoir gradually warms to approximately 15–19°C. In summer, particularly in January and February, near-surface temperatures may reach about 20–24°C on warm, settled days. By autumn, temperatures usually ease back to between 15 and 19°C. Rainfall and wind can cause short-term variations in surface conditions.
Swimming Conditions
Swimming is not allowed at Cosseys Reservoir. As it is part of Auckland’s public water supply system, access to the water is restricted to protect water quality and public health. While summer temperatures may appear suitable for swimming, the reservoir is managed specifically for drinking water storage rather than recreation. Visitors can enjoy walking tracks, scenic views and picnic areas within the surrounding park, but entering the water is prohibited. These restrictions help maintain safe drinking water standards for the wider Auckland community.