Port Underwood – current water temperature and swimming conditions

Water Temperature in Port Underwood: Daily Trends, Historical Records, and Forecast

⚠️ This is cool water that may feel brisk on entry. Swimming is usually limited to short sessions, and prolonged stays can become uncomfortable without thermal protection. Many swimmers choose a wetsuit, especially for surfing or open-water swimming.

It’s important to note that these swimming tips and recommendations apply only in settled weather. When air temperatures drop below 20°C — and sometimes even below 25°C — swimming can feel uncomfortable, even when water temperatures are relatively high.

Water Temperature Over the Last 30 Days

While water temperatures in Port Underwood declined overall during the past month, they have shown a noticeable rebound over the last week.

According to our forecast, Sea water temperature in Port Underwood will be 14.5°C in the next 7 days. See the table below for daily data for the upcoming week.

Table of Daily Sea Temperature Data

Annual Water Temperature Overview by Month

Monthly Water Temp Ranges

30°C

25°C

20°C

15°C

10°c

5°C

0°C

Annual Water Temperature Trend

Port Underwood is a sheltered inlet on the eastern side of the Marlborough Region, opening into Cook Strait. Compared to more exposed stretches of coast, the bay can offer slightly calmer conditions, though it still reflects the cool, tidal waters of the strait. In winter, from June to August, sea temperatures generally range between 9–12°C, which feels distinctly cold and is usually only comfortable for hardy swimmers or those wearing full wetsuits. Through spring, temperatures gradually lift to around 11–14°C. Summer, from December to March, brings the mildest conditions, with water temperatures commonly sitting between 15–18°C during settled spells. Early autumn can still see 14–16°C before cooling again as winter approaches.