Delaware Bay – current water temperature and swimming conditions

This page shows the current water temperature at Delaware Bay in Nelson Region. You can view recent sea temperature trends on a 30-day chart, check typical monthly water temperature ranges, and compare today’s reading with historical averages for this date. The page also includes a 7-day water temperature forecast, nearby beaches with similar conditions, local weather information, and a summary of swimming conditions to help you assess how suitable the water is for swimming.

Current Sea Water Temperature

18.9°C

Today

18.8°C

Yesterday

18.8°C

A Week Ago

The average sea water temperature today in Delaware Bay is about 19°C.

Water Temperature in Delaware Bay: Daily Trends, Historical Records, and Forecast

⚠️ Water in this range feels cool but still manageable for many swimmers. Short to moderate swims are comfortable, especially in warm weather. Some people may prefer a wetsuit for longer stays, particularly when swimming actively or outside peak summer conditions.

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

From February 27 to March 29

Water temperatures in Delaware Bay have been on a steady rise over the past month and have continued to climb over the last week.

According to our forecast, Sea water temperature in Delaware Bay will be 15.3°C in the next 7 days. See the table below for daily data for the upcoming week.

Table of Daily Sea Temperature Data

Date	Current	Average	Forecast
Mar 22	18.9°C	16.8°C
Mar 23	18.8°C	16.5°C
Mar 24	18.8°C	16.3°C
Mar 25	18.7°C	16.5°C
Mar 26	19.0°C	16.8°C
Mar 27	19.0°C	16.3°C
Mar 28	18.9°C	16.5°C
Mar 29	18.8°C	16.8°C
Mar 30	18.9°C	16.8°C	18.9°C
Mar 31		15.5°C	18.4°C
Apr 1		15.3°C	17.9°C
Apr 2		14.8°C	17.4°C
Apr 3		14.0°C	16.9°C
Apr 4		13.8°C	16.4°C
Apr 5		13.8°C	15.8°C
Apr 6		13.8°C	15.3°C

* Current - Actual water temperature value

** Average - Average water temperature on this day in recent years

*** Forecast - Our water temperature forecast

Actual near-shore water temperatures in Delaware Bay can vary by several degrees from the values shown, particularly after heavy rain, strong southerlies, or prolonged windy conditions. Certain wind patterns can trigger upwelling, where cooler, deeper water is pushed to the surface and replaces the warmer top layer, leading to noticeable short-term changes in water temperature.

Our water temperature forecast is produced using a proprietary mathematical model that combines real-time measurements with long-term historical patterns, local weather conditions, wind strength and direction, and air temperature specific to each coastal region. To improve accuracy, we cross-check data from nearby locations and use multiple sources, including offshore buoys, satellite-based sea surface maps, and observations provided by local authorities.

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

Delaware Bay lies northeast of Nelson, opening into Cook Strait and bordered by rolling hills and farmland. Water temperatures here reflect the tidal exchange between the sheltered inner bay and the cooler strait beyond. In winter, from June to August, the sea generally ranges 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 rise to around 11–14°C. Summer, from December to March, brings the mildest conditions, with water temperatures commonly sitting between 16–19°C during settled, sunny spells. Early autumn can still see 15–17°C before cooling again as winter approaches.

Monthly Water Temperature Range (Min, Max & Average)

Month	Min	Avg	Max
January	14°C	16°C	19°C
February	14°C	17°C	19°C
March	14°C	16°C	19°C
April	12°C	15°C	17°C
May	11°C	14°C	17°C
June	10°C	13°C	16°C
July	10°C	12°C	15°C
August	9°C	12°C	14°C
September	10°C	12°C	14°C
October	10°C	13°C	15°C
November	11°C	14°C	16°C
December	13°C	15°C	18°C

* Click on a month to view detailed water temperature data.

Delaware Bay: Weather Forecast

March 30

11°C / 24°C

overcast clouds: 85-100%

humidity: 86% | wind: 4 kmh

March 31

8°C / 12°C

overcast clouds: 85-100%

humidity: 76% | wind: 7 kmh

April 1

8°C / 16°C

clear sky

humidity: 71% | wind: 4 kmh

April 2

11°C / 22°C

clear sky

humidity: 75% | wind: 7 kmh

Local Water Conditions and Nearby Spots

Swimming Conditions

Swimming is allowed at various access points around Delaware Bay, particularly at sandy and gently sloping areas. The bay’s curved shape often means calmer conditions than fully exposed Cook Strait beaches, especially on light wind days. However, tidal currents can be noticeable, and wind can quickly create chop across the surface. There are generally no regular lifeguard patrols, so swimmers should assess the sea state carefully before entering. During summer, the relatively warmer and sheltered water can be enjoyable for families and confident swimmers. Outside the warmer season, thermal gear is recommended, as the water remains cool year-round despite the partial shelter offered by the bay.