Lake Rotoiti Tasman – current water temperature and swimming conditions
This page provides information about the current water temperature at Lake Rotoiti Tasman 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 Lake Rotoiti Tasman today is 15°C.
Water Temperature in Lake Rotoiti Tasman: 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
While water temperatures in Lake Rotoiti Tasman declined overall during the past month, they have shown a noticeable rebound over the last week.
According to our forecast, the water temperature in Lake Rotoiti Tasman will be 11.1°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 |
|---|---|---|---|
| Mar 22 | 14.0°C | 10.6°C | |
| Mar 23 | 14.0°C | 10.6°C | |
| Mar 24 | 14.0°C | 10.6°C | |
| Mar 25 | 14.0°C | 10.6°C | |
| Mar 26 | 14.2°C | 10.6°C | |
| Mar 27 | 14.2°C | 10.6°C | |
| Mar 28 | 14.2°C | 10.6°C | |
| Mar 29 | 14.2°C | 10.6°C | |
| Mar 30 | 14.5°C | 10.6°C | 14.5°C |
| Mar 31 | 10.6°C | 14.0°C | |
| Apr 1 | 10.6°C | 13.5°C | |
| Apr 2 | 10.6°C | 13.0°C | |
| Apr 3 | 10.6°C | 12.6°C | |
| Apr 4 | 10.6°C | 12.1°C | |
| Apr 5 | 10.6°C | 11.6°C | |
| Apr 6 | 10.6°C | 11.1°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 Australia.
Monthly Water Temperature Range (Min, Max & Average)
| Month | Today | Yesterday | A Week Ago |
|---|---|---|---|
| January | 6°C | 12°C | 17°C |
| February | 8°C | 12°C | 17°C |
| March | 7°C | 11°C | 14°C |
| April | 4°C | 12°C | 19°C |
| May | 3°C | 7°C | 11°C |
| June | 1°C | 5°C | 9°C |
| July | 0°C | 4°C | 8°C |
| August | 1°C | 5°C | 8°C |
| September | 2°C | 7°C | 11°C |
| October | 3°C | 7°C | 10°C |
| November | 5°C | 9°C | 13°C |
| December | 6°C | 10°C | 14°C |
Lake Rotoiti Tasman: Weather Forecast
March 30
March 31
April 1
April 2
April 3
Location & Local Information
Lake Rotoiti, in the Tasman Region within Nelson Lakes National Park, is a deep alpine lake surrounded by forested mountains and the township of St Arnaud. Fed by cold mountain streams, its water temperature remains low for much of the year. In winter, surface temperatures are generally around 5–8°C. During spring, snowmelt from surrounding peaks keeps the lake brisk, typically between 7 and 11°C. In summer, particularly in January and February, near-shore areas may warm to approximately 12–17°C on calm, sunny days, while deeper water remains significantly colder. By autumn, temperatures usually ease back to between 8 and 13°C. Wind can quickly influence surface conditions on this long, open lake.
Swimming Conditions
Swimming is allowed at accessible shoreline spots, including near the jetty and beaches around St Arnaud. The most comfortable time for a swim is during settled mid to late summer weather when temperatures approach the mid to high teens and winds are light. Even then, the water can feel cold due to its alpine origin, so gradual entry is recommended. Swimmers should choose sheltered bays and avoid windy conditions, as waves can develop quickly. Checking local weather conditions beforehand helps ensure a safer and more enjoyable experience.