Lake Rotoroa – current water temperature and swimming conditions
This page provides information about the current water temperature at Lake Rotoroa 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 Rotoroa today is 12°C.
Water Temperature in Lake Rotoroa: 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 Rotoroa 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 Rotoroa will be 10.3°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 | 12.2°C | 10.1°C | |
| May 7 | 13.5°C | 10.1°C | |
| May 8 | 13.8°C | 10.1°C | |
| May 9 | 13.8°C | 10.1°C | |
| May 10 | 14.1°C | 10.1°C | |
| May 11 | 14.1°C | 10.1°C | |
| May 12 | 12.4°C | 10.1°C | |
| May 13 | 12.4°C | 10.1°C | |
| May 14 | 11.9°C | 10.1°C | 11.9°C |
| May 15 | 10.1°C | 11.7°C | |
| May 16 | 10.1°C | 11.5°C | |
| May 17 | 10.1°C | 11.2°C | |
| May 18 | 10.1°C | 11.0°C | |
| May 19 | 10.1°C | 10.8°C | |
| May 20 | 10.1°C | 10.6°C | |
| May 21 | 10.1°C | 10.3°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 | 16°C | 21°C |
| February | 12°C | 17°C | 21°C |
| March | 9°C | 14°C | 19°C |
| April | 8°C | 13°C | 17°C |
| May | 6°C | 10°C | 14°C |
| June | 3°C | 8°C | 12°C |
| July | 3°C | 7°C | 10°C |
| August | 3°C | 7°C | 10°C |
| September | 5°C | 9°C | 12°C |
| October | 6°C | 9°C | 12°C |
| November | 8°C | 12°C | 16°C |
| December | 9°C | 14°C | 18°C |
Lake Rotoroa: Weather Forecast
May 15
May 16
May 17
May 18
May 19
Location & Local Information
Lake Rotoroa, in the Tasman Region within Nelson Lakes National Park, is a deep alpine lake surrounded by forested mountains. Fed by cold mountain streams and subject to a cool inland climate, 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 affect surface conditions on this long, narrow lake.
Swimming Conditions
Swimming is allowed at accessible shoreline spots, including areas near the township of St Arnaud and campgrounds. 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.