Cobb Reservoir – current water temperature and swimming conditions
This page provides information about the current water temperature at Cobb Reservoir in Tasman 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 Cobb Reservoir today is 10°C.
Water Temperature in Cobb Reservoir: Daily Trends, Historical Records, and Forecast
❌ Lake water below 10°C is extremely cold and generally unsuitable for swimming for most people. Even during warm weather, deep lakes retain cold water, making entry uncomfortable and limiting time in the water. Swimming at this temperature is usually limited to quick dips or cold-water enthusiasts. Cool air temperatures or cloudy conditions can make lake swimming particularly harsh.
Water Temperature Over the Last 30 Days
Water temperatures in Cobb 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 Cobb Reservoir will be 9.5°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 6 | 11.2°C | 9.5°C | |
| May 7 | 11.2°C | 9.5°C | |
| May 8 | 11.6°C | 9.5°C | |
| May 9 | 11.6°C | 9.5°C | |
| May 10 | 11.9°C | 9.5°C | |
| May 11 | 11.9°C | 9.5°C | |
| May 12 | 10.4°C | 9.5°C | |
| May 13 | 10.4°C | 9.5°C | |
| May 14 | 9.7°C | 9.5°C | 9.7°C |
| May 15 | 9.5°C | 9.7°C | |
| May 16 | 9.5°C | 9.7°C | |
| May 17 | 9.5°C | 9.6°C | |
| May 18 | 9.5°C | 9.6°C | |
| May 19 | 9.5°C | 9.6°C | |
| May 20 | 9.5°C | 9.6°C | |
| May 21 | 9.5°C | 9.5°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 | 11°C | 18°C | 24°C |
| February | 9°C | 17°C | 24°C |
| March | 10°C | 16°C | 22°C |
| April | 9°C | 14°C | 18°C |
| May | 5°C | 10°C | 14°C |
| June | 2°C | 7°C | 12°C |
| July | 1°C | 6°C | 10°C |
| August | 3°C | 7°C | 11°C |
| September | 5°C | 9°C | 13°C |
| October | 7°C | 12°C | 16°C |
| November | 8°C | 14°C | 19°C |
| December | 9°C | 15°C | 21°C |
Cobb Reservoir: Weather Forecast
May 15
May 16
May 17
May 18
May 19
Location & Local Information
Cobb Reservoir, in the Tasman Region within Kahurangi National Park, is a high-country hydro lake set among open tussock and rugged mountains. Its elevation and alpine inflows influence water temperatures throughout the year. In winter, surface temperatures are generally around 4–8°C, with frost and occasional ice forming along the shoreline. During spring, snowmelt from surrounding peaks keeps the reservoir cold, typically between 6 and 10°C. In summer, particularly in January and February, sheltered near-shore areas may warm to approximately 11–16°C on calm, sunny days, while deeper water remains noticeably colder. By autumn, temperatures usually ease back to between 7 and 12°C. Strong winds can mix the surface and reduce comfort levels.
Swimming Conditions
Swimming is allowed at Cobb Reservoir, but it is uncommon due to the consistently cool conditions and remote setting. Even in mid-summer, the water can feel brisk, especially away from the shoreline. The most suitable time for a brief swim is during settled summer weather when temperatures approach the mid teens and winds are light. Swimmers should choose sheltered bays and enter gradually to reduce the risk of cold shock. Checking weather conditions beforehand helps ensure a safer and more comfortable experience in this exposed alpine environment.