Marine Heatwave Live NZA Data Experiment, by Marulho ↗

How warm is the sea today?

A live dashboard tracking sea surface temperature (SST), 30-year anomaly, and marine-heatwave status across 12 NZ coastal regions — updated daily.

What's a marine heatwave?

Sea temperature in the warmest 10% of the 30-year record for at least 5 consecutive days. Slower and larger than a land heatwave, often invisible from shore — but linked to kelp forest die-off, mass marine mortality, and disrupted fisheries.

6 regions currently in marine heatwave conditions. Longest active event: 93 days in Fiordland (Strong category).

Latest observation: 2026-06-20 — live sea temperature from Open-Meteo Marine API — 30-year average from NOAA CoralTemp (1991–2020)

Active strong marine heatwave, day 28.

Northland

Te Tai Tokerau

Strong

Off Bay of Islands

17.7°C

+1.1°C vs baseline

Day 28 of heatwave · peak +1.4°C

60-day sea temperature trend for Northland: 2026-04-22 to 2026-06-20. Sea temperature ranged from 17.7°C to 19.8°C. 26 days above threshold.30-year seasonal climatology (1991–2020 NOAA CoralTemp): the historical mean SST for each day-of-year. The line slopes with the season.Marine heatwave threshold: the 90th percentile of historical SST for each day-of-year (Hobday et al. 2016, 1991–2020 baseline). SST above this line for ≥5 consecutive days is a heatwave.
30-yr baseline 16.6° · heatwave threshold 17.5°
Sea temperature at or below the 30-year average.

Hauraki Gulf

Tīkapa Moana

Off Auckland

14.9°C

-1.0°C vs baseline

No active heatwave

60-day sea temperature trend for Hauraki Gulf: 2026-04-22 to 2026-06-20. Sea temperature ranged from 14.9°C to 18.3°C.30-year seasonal climatology (1991–2020 NOAA CoralTemp): the historical mean SST for each day-of-year. The line slopes with the season.Marine heatwave threshold: the 90th percentile of historical SST for each day-of-year (Hobday et al. 2016, 1991–2020 baseline). SST above this line for ≥5 consecutive days is a heatwave.
30-yr baseline 15.9° · heatwave threshold 16.6°
Sea temperature at or below the 30-year average.

Coromandel

Off Coromandel township

14.3°C

-1.1°C vs baseline

No active heatwave

60-day sea temperature trend for Coromandel: 2026-04-22 to 2026-06-20. Sea temperature ranged from 14.3°C to 18.3°C.30-year seasonal climatology (1991–2020 NOAA CoralTemp): the historical mean SST for each day-of-year. The line slopes with the season.Marine heatwave threshold: the 90th percentile of historical SST for each day-of-year (Hobday et al. 2016, 1991–2020 baseline). SST above this line for ≥5 consecutive days is a heatwave.
30-yr baseline 15.4° · heatwave threshold 16.1°
Active strong marine heatwave, day 22.

Bay of Plenty

Te Moana-a-Toi

Strong

Off Ōpōtiki

16.2°C

+0.9°C vs baseline

Day 22 of heatwave · peak +1.3°C

60-day sea temperature trend for Bay of Plenty: 2026-04-22 to 2026-06-20. Sea temperature ranged from 16.2°C to 19.2°C. 22 days above threshold.30-year seasonal climatology (1991–2020 NOAA CoralTemp): the historical mean SST for each day-of-year. The line slopes with the season.Marine heatwave threshold: the 90th percentile of historical SST for each day-of-year (Hobday et al. 2016, 1991–2020 baseline). SST above this line for ≥5 consecutive days is a heatwave.
30-yr baseline 15.3° · heatwave threshold 16.2°
Sea temperature at or below the 30-year average.

East Cape

East of Te Araroa

15.9°C

-0.1°C vs baseline

No active heatwave

60-day sea temperature trend for East Cape: 2026-04-22 to 2026-06-20. Sea temperature ranged from 15.8°C to 18.5°C.30-year seasonal climatology (1991–2020 NOAA CoralTemp): the historical mean SST for each day-of-year. The line slopes with the season.Marine heatwave threshold: the 90th percentile of historical SST for each day-of-year (Hobday et al. 2016, 1991–2020 baseline). SST above this line for ≥5 consecutive days is a heatwave.
30-yr baseline 15.9° · heatwave threshold 16.8°
Sea temperature at or below the 30-year average.

Hawke's Bay / Wairarapa

Te Matau-a-Māui

Off Napier

14.0°C

-0.8°C vs baseline

No active heatwave

60-day sea temperature trend for Hawke's Bay / Wairarapa: 2026-04-22 to 2026-06-20. Sea temperature ranged from 14.0°C to 16.3°C.30-year seasonal climatology (1991–2020 NOAA CoralTemp): the historical mean SST for each day-of-year. The line slopes with the season.Marine heatwave threshold: the 90th percentile of historical SST for each day-of-year (Hobday et al. 2016, 1991–2020 baseline). SST above this line for ≥5 consecutive days is a heatwave.
30-yr baseline 14.8° · heatwave threshold 15.8°
Sea temperature above the 30-year average.

Marlborough Sounds

Pelorus Sound

13.4°C

+0.5°C vs baseline

No active heatwave

60-day sea temperature trend for Marlborough Sounds: 2026-04-22 to 2026-06-20. Sea temperature ranged from 13.4°C to 16.1°C. 1 day above threshold.30-year seasonal climatology (1991–2020 NOAA CoralTemp): the historical mean SST for each day-of-year. The line slopes with the season.Marine heatwave threshold: the 90th percentile of historical SST for each day-of-year (Hobday et al. 2016, 1991–2020 baseline). SST above this line for ≥5 consecutive days is a heatwave.
30-yr baseline 13.0° · heatwave threshold 13.7°
Sea temperature above the 30-year average.

Golden Bay

Mohua

Mid-bay

13.8°C

+0.5°C vs baseline

No active heatwave

60-day sea temperature trend for Golden Bay: 2026-04-22 to 2026-06-20. Sea temperature ranged from 13.8°C to 16.3°C. 5 days above threshold.30-year seasonal climatology (1991–2020 NOAA CoralTemp): the historical mean SST for each day-of-year. The line slopes with the season.Marine heatwave threshold: the 90th percentile of historical SST for each day-of-year (Hobday et al. 2016, 1991–2020 baseline). SST above this line for ≥5 consecutive days is a heatwave.
30-yr baseline 13.2° · heatwave threshold 13.9°
Active strong marine heatwave, day 7.

Kaikōura / East Coast South

Strong

East of Kaikōura

12.9°C

+1.5°C vs baseline

Day 7 of heatwave · peak +1.5°C

60-day sea temperature trend for Kaikōura / East Coast South: 2026-04-22 to 2026-06-20. Sea temperature ranged from 12.2°C to 15.4°C. 15 days above threshold.30-year seasonal climatology (1991–2020 NOAA CoralTemp): the historical mean SST for each day-of-year. The line slopes with the season.Marine heatwave threshold: the 90th percentile of historical SST for each day-of-year (Hobday et al. 2016, 1991–2020 baseline). SST above this line for ≥5 consecutive days is a heatwave.
30-yr baseline 11.5° · heatwave threshold 12.3°
Active severe marine heatwave, day 91.

Otago

Severe

East of the peninsula

12.2°C

+1.8°C vs baseline

Day 91 of heatwave · peak +2.0°C

60-day sea temperature trend for Otago: 2026-04-22 to 2026-06-20. Sea temperature ranged from 12.2°C to 13.7°C. 60 days above threshold.30-year seasonal climatology (1991–2020 NOAA CoralTemp): the historical mean SST for each day-of-year. The line slopes with the season.Marine heatwave threshold: the 90th percentile of historical SST for each day-of-year (Hobday et al. 2016, 1991–2020 baseline). SST above this line for ≥5 consecutive days is a heatwave.
30-yr baseline 10.3° · heatwave threshold 11.2°
Active strong marine heatwave, day 93.

Fiordland

Te Rua-o-te-Moko

Strong

West of Milford

14.7°C

+2.0°C vs baseline

Day 93 of heatwave · peak +2.3°C

60-day sea temperature trend for Fiordland: 2026-04-22 to 2026-06-20. Sea temperature ranged from 14.6°C to 15.8°C. 60 days above threshold.30-year seasonal climatology (1991–2020 NOAA CoralTemp): the historical mean SST for each day-of-year. The line slopes with the season.Marine heatwave threshold: the 90th percentile of historical SST for each day-of-year (Hobday et al. 2016, 1991–2020 baseline). SST above this line for ≥5 consecutive days is a heatwave.
30-yr baseline 12.7° · heatwave threshold 13.4°
Active extreme marine heatwave, day 57.

Foveaux Strait

Te Ara-a-Kiwa

Extreme

Between Bluff and Stewart Island

13.3°C

+2.3°C vs baseline

Day 57 of heatwave · peak +2.3°C

60-day sea temperature trend for Foveaux Strait: 2026-04-22 to 2026-06-20. Sea temperature ranged from 13.2°C to 14.6°C. 57 days above threshold.30-year seasonal climatology (1991–2020 NOAA CoralTemp): the historical mean SST for each day-of-year. The line slopes with the season.Marine heatwave threshold: the 90th percentile of historical SST for each day-of-year (Hobday et al. 2016, 1991–2020 baseline). SST above this line for ≥5 consecutive days is a heatwave.
30-yr baseline 10.9° · heatwave threshold 11.7°

About marine heatwaves

Past NZ events have stretched thousands of kilometres across the Tasman Sea. Documented impacts around Aotearoa and elsewhere include kelp forest die-off, mass mortality in marine life, lower dissolved oxygen, ocean acidification, disrupted fisheries and aquaculture, and shifts in where species can survive — sometimes compounding with land heatwaves and other climate extremes.

This page reports the data so anyone can see when local conditions cross into heatwave territory. Interpretation of what it means for any specific ecosystem belongs with marine biologists, not us.