Lake Grassmere – current water temperature and swimming conditions
This page provides information about the current water temperature at Lake Grassmere in Marlborough 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 Lake Grassmere today is 13°C.
Water Temperature in Lake Grassmere: 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 Lake Grassmere 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 Lake Grassmere will be 12.1°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 | 13.6°C | 12.0°C | |
| May 7 | 15.1°C | 12.0°C | |
| May 8 | 15.8°C | 12.0°C | |
| May 9 | 15.8°C | 12.0°C | |
| May 10 | 16.1°C | 12.0°C | |
| May 11 | 16.1°C | 12.0°C | |
| May 12 | 15.6°C | 12.0°C | |
| May 13 | 15.6°C | 12.0°C | |
| May 14 | 13.1°C | 12.0°C | 13.1°C |
| May 15 | 12.0°C | 13.0°C | |
| May 16 | 12.0°C | 12.8°C | |
| May 17 | 12.0°C | 12.7°C | |
| May 18 | 12.0°C | 12.6°C | |
| May 19 | 12.0°C | 12.4°C | |
| May 20 | 12.0°C | 12.3°C | |
| May 21 | 12.0°C | 12.1°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 | 15°C | 20°C | 25°C |
| February | 15°C | 20°C | 25°C |
| March | 14°C | 18°C | 22°C |
| April | 10°C | 15°C | 19°C |
| May | 7°C | 12°C | 17°C |
| June | 5°C | 10°C | 14°C |
| July | 5°C | 9°C | 12°C |
| August | 6°C | 9°C | 12°C |
| September | 7°C | 11°C | 15°C |
| October | 9°C | 14°C | 18°C |
| November | 10°C | 16°C | 22°C |
| December | 13°C | 19°C | 24°C |
Lake Grassmere: Weather Forecast
May 15
May 16
May 17
May 18
Location & Local Information
Lake Grassmere, also known as Kapara Te Hau, in the Marlborough Region near the east coast, is a shallow coastal lagoon separated from the sea by a narrow gravel barrier. Much of the surrounding area is used for salt production, and the lake’s shallow depth strongly influences its water temperature. In winter, surface temperatures are generally around 8–12°C. During spring, the lagoon gradually warms to approximately 12–18°C as air temperatures rise. In summer, particularly in January and February, shallow areas can reach about 20–26°C on hot, settled days. By autumn, temperatures usually ease back to between 14 and 19°C. Wind can quickly mix the shallow water and affect surface warmth.
Swimming Conditions
Swimming is not recommended at Lake Grassmere. Although summer water temperatures may feel warm enough for swimming, the lake is managed primarily for salt harvesting, and access to much of the area is restricted. Water salinity levels can also vary significantly, and conditions are not suited to recreational use. Visitors generally view the lake from roadside lookouts rather than entering the water. For most people, Lake Grassmere is appreciated for its unique landscape and saltworks rather than as a swimming destination.