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

15.1°C

Today

15.9°C

Yesterday

17.7°C

A Week Ago

The water temperature in Cosseys Reservoir today is 15°C.

Water Temperature in Cosseys Reservoir: Daily Trends, Historical Records, and Forecast

⚠️ A lake temperature of 15 to 20°C is considered cool to comfortable for swimming in Australia. On warm days with light winds, this range allows for relaxed swimming, especially in shallow or sheltered areas. Comfort depends strongly on air temperature and sunshine, as cooler or overcast weather can still make the water feel chilly. This range is common during spring and early summer.

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 14.9°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
May 7	16.9°C	14.9°C
May 8	16.9°C	14.9°C
May 9	17.7°C	14.9°C
May 10	17.7°C	14.9°C
May 11	16.3°C	14.9°C
May 12	16.3°C	14.9°C
May 13	17.8°C	14.9°C
May 14	15.9°C	14.9°C
May 15	15.1°C	14.9°C	15.1°C
May 16		14.9°C	15.1°C
May 17		14.9°C	15.1°C
May 18		14.9°C	15.0°C
May 19		14.9°C	15.0°C
May 20		14.9°C	15.0°C
May 21		14.9°C	15.0°C
May 22		14.9°C	14.9°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

May 15

7°C / 15°C

clear sky

rain: 0% | wind: 11 km/h

May 16

6°C / 15°C

clear sky

rain: 0% | wind: 13 km/h

May 17

7°C / 15°C

mainly clear

rain: 0% | wind: 14 km/h

May 18

8°C / 15°C

clear sky

rain: 0% | wind: 11 km/h

May 19

7°C / 16°C

clear sky

rain: 0% | wind: 10 km/h

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.

Nearby Lakes

Frequently Asked Questions

What is the current water temperature in Cosseys Reservoir?

The water temperature in Cosseys Reservoir today is 15°C.

What is the water temperature in Cosseys Reservoir during the summer months?

In summer, water temperatures in Cosseys Reservoir at Wangi Wangi typically range from 16°C to 25°C.

Is it possible to swim in Cosseys Reservoir (Auckland Region)?

Swimming at Cosseys Reservoir is generally not recommended — many reservoirs in the Auckland Region form part of the drinking‑water network or have steep banks, submerged hazards and access restrictions, so check on‑site signage and Auckland Council rules before entering. If swimming is permitted, the water can be cold and visibility poor year‑round, so never swim alone and consider using designated swimming spots instead.