Mercator Ocean International
Ocean Temperature Bulletin

Ocean Temperature Bulletin
July 2026

Mercator Ocean International (MOi) oceanographers examine marine heatwaves across the global ocean. They analyse a variety of datasets from observation analyses
(satellite sea surface temperature maps) to model analyses
(assimilating satellite and in situ observations) and model forecasts.¹

All images in this article can be used freely and should be credited with the following information :
Image source: European Union, Copernicus Marine Service Data 2025 © Mercator Ocean .

Key takeaway

Global ocean 

  • July 2026 was the warmest July on record for the global ocean (between 60°S and 60°N) with a mean Sea Surface Temperature (SST) of 21.00 ± 0.11°C. 
  • 79% of the global ocean registered above average monthly SSTs, and 24% of the global ocean registered above average values of at least 1°C. Regions in the tropical Pacific, subtropical North Atlantic and surrounding western Europe were most affected.
  • Intense marine heatwaves (strong or higher intensities) have covered 27% of the surface of the ocean for at least 1 day during July 2026, being the widest extent of the last 34 years, far exceeding the previous record set in 2024 (22 %).
  • El Niño continued to intensify, with temperatures exceeding 2°C and 3°C above average, from Central America to the Peruvian coast.

Europe

  • In the Mediterranean Sea also registered the warmest July on record with a mean SST of 27.07 ± 0.27°C , warmer than previous record of July 2025 (26.68 ± 0.11 °C). A record of 79% of the basin was affected by intense marine heatwaves for at least 1 day, far ahead of July 2025 with 70%. Marine heatwaves in the Mediterranean Sea lasted the longest in July 2026 for a July month.
  • In the North Atlantic (between 0°N and 60°N), July 2026 was the 3rd warmest July on record and the 3rd most extreme in terms of marine heatwave conditions. 31% of the region was impacted by strong, or higher intensity marine heatwaves for at least 1 day. This corresponds to the 3rd largest extent of the last 34 years for a July month, behind 2024 and 2023. 

sea Surface Temperature

Daily sea surface temperatures averaged for the global ocean (left), the Mediterranean Sea (middle) and the North Atlantic Ocean (right) between 1991-2020 using ESA’s Climate Change Initiative (grey shades), and between 2021-2026 (coloured shades) using Mercator Ocean International’s GLO12 analysis and forecast.

  • July 2026 was the warmest July on record for the global ocean (between 60°S and 60°N) with a mean Sea Surface Temperature (SST) of 21.00 ± 0.11°C , surpassing the previous record set in 2023 (20.92±0.06°C). 
  • Regionally, for the Mediterranean Sea, July 2026 was also the warmest July on record, with a mean SST of 27.07 ± 0.27°C , warmer than previous record of July 2025 (26.68 ± 0.11 °C). 
  • For the North Atlantic (between 0°N and 60°N), July 2026 was the 3rd warmest July month with a mean SST of 24.15 ± 0.25°C, the record being July 2023 (24.77 ± 0.12°C). 

 

SEA SURFACE TEMPERATURE ANOMALIES

Mean SST anomaly in July 2026 relative to a 30-year climatology (1993-2022), calculated using daily data from Mercator Ocean International’s GLO12 analysis and forecasting system for 2026 and from the GLORYS12 reanalysis for the climatological mean.

 

 

In July 2026, 79% of the global ocean (between 60°S and 60°N) show above average mean SSTs, and 24% of the global ocean was bove average by at least 1°C.

  • Most of the Mediterranean Sea (94%) showed above-average SSTs, with stronger SSTs in the western part, reaching 3°C.
  • The North Pacific Ocean has seen sea surface temperatures (SSTs) that were mostly above average, covering a band in the Sea of Japan and in the central North Pacific, reaching or even exceeding 3 °C above average. In the eastern region between Hawaii and Mexico, SSTs are more than 2 °C above average. In the South Pacific, SSTs are close to 2°C above average around New Zealand, as well as off the coast of Chile. To the south-east of Australia, temperatures are slightly above average.
  • In the Equatorial Pacific, the entire band between 180°W and the coast of South America is characterised by high SSTs, ranging from 2°C to over 3°C above average. These above-average SSTs extend from Central America to the Peruvian coast. This development marks the intensification of the El Niño. The North Atlantic, A broad band of above-average SSTs stretches across the basin, from the Caribbean to western and northern Europe, where the anomalies exceed 3°C, particularly in the Bay of Biscay and the North Sea . Mid-latitudes showed below-average SSTs, between the Canadian coast and 30°W (“cold blob” region)
  • The South Atlantic showed below average temperature on the eastern part along the African coast, as well as patchy above-average SSTs across the entire width of the basin, between 30°S and 50°S
  • In the Indian Ocean, above-average sea surface temperatures (SSTs) are being observed to the east and north of Madagascar, and to the west of Indonesia, where they are locally around 2 °C above average.

 

RANKING JULY 2026 SST

Ranking of July’s sea surface temperature against previous July months of the historical period since 1993. The ranking is based on July monthly SST averages between 1993 and 2026.

 

 

  • Around 16% of the global ocean (between 60°S and 60°N) ranked as the warmest July month on record, with regions in the tropical Pacific, subtropical North Atlantic and surrounding western Europe most affected.
  • Regions such as the south-western Pacific (around New Zealand) and the southern part of the Bering Sea is also characterised by vast areas where July was the hottest on record.
  • 27% of the Mediterranean Sea ranked as the warmest July month on record and 70% of its area was among the four warmest Julys on record.
     
Ranking of July’s sea surface temperature against previous July months of the historical period since 1993 In the North Atlantic (0°N-60°N). The ranking is based on July monthly SST averages between 1993 and 2026.

 

Ranking of July’s sea surface temperature against previous July months of the historical period since 1993 in the Pacific Ocean (30°S-30°N). The ranking is based on July monthly SST averages between 1993 and 2026.

 

Ongoing Marine Heatwaves

Month of onset for the ongoing MHWs on the 30th of July 2026. The colours indicate the month during which the MHW started. For instance, ocean pixels in red correspond to an MHW that developed during Julyl 2026 and are less than one month old, in orange MHW between 1 and 2 months old, etc.

 

  • On the 31st of July, 37% of the global ocean (between 60°S and 60°N) was affected by MHWs.  
  • The majority of these MHWs developed recently, with 23% of the global Ocean (between 60°S and 60°N) affected by MHWs less than 1 month old and 14% by events more than 1 month old.
  • Widespread and persistent MHWs are found in the central Pacific, spanning the entire width of the basin, with the oldest MHW developed in December-January in the south of California.  In the South Pacific, around New Zealand, MHWs reached 3 or 4 months
  • In the Southern Ocean, between 60°E and 90°E, persistent MHWs are also being observed, which can last for up to 3 to 4 months. In very localised areas, some MHWs have persisted since January.

Total Surface Marine Heatwaves

Global Ocean (60°S and 60°N)

 

Surface occupied by MHWs in the global ocean (between 60°S and 60°N) between August 2025 and July 2026 based on daily monitoring. The black solid line represents the total surface of MHW, while the coloured lines represent the surface of each MHW category. The grey background highlights the month of July 2026.

 

 

 

  • In July 2026, the total surface area of MHW (black line) increased from 32% to 37% of the global ocean (between 60°S and 60°N. 
  • The majority of MHWs events were of moderate categories (around 23% to 25% of the global ocean) with strong category events increasing steadily across the month to reach around 10-11% of the global ocean. 
  • For comparison, the total surface occupied by MHWs at the end of July 2025 was notably lower (~22% by the end of the month).

 

Mediterranean Sea

Surface occupied by MHWs in the Mediterranean Sea between August 2025 and July 2026 based on daily monitoring. The black solid line represents the total surface of MHW, while the coloured lines represent the surface of each MHW category. The grey background highlights the month of July 2026.

 

 

 

  • As regards the Mediterranean Sea, the total area covered by MHWs decreased during July 2026, dropping from 73% to 54%, although it reached a peak of 75% in the middle of the month. Towards the end of the month, the trend was upwards, increasing from 44% to 54% over the last five days. 
  • These MHWs were mainly of moderate and strong category. This peak was characterized by a significant increase of severe and extreme categories (respectively  11% and more than 1%). 
  • For comparison, the total surface occupied by MHWs at the end of July 2025 was notably lower, with 14%, but this came after a whole month of decrease in area, with a fall of more than 65% at the start of the month. 

 

North Atlantic (between 0°N and 60°N) 

Surface occupied by MHWs in the North Atlantic (between 0°N and 60°N) between August 2025 and July 2026 based on daily monitoring. The black solid line represents the total surface of MHW, while the coloured lines represent the surface of each MHW category. The grey background highlights the month of July 2026.

 

  • In the North Atlantic (between 0°N and 60°N), the total surface area of MHW increased significantly during the first half of the month to reach more than 34%.
  •  In the second half of the month, it decreased to 27%, and a second increase in the last few days of the month, with a total surface area of MHW up to 30%.
  • These events are predominantly of moderate (17%-22%) and strong (5%-10%), with a peak of severe category at the middle of the month, reaching close to 5% of the total surface area.

Total Number Marine Heatwaves

 MHW days of strong and higher category in July 2026. Number of days during which a MHW of strong, severe or extreme category  occurred in the past month. Blank areas mean that no MHW of strong or higher category happened during the month. Blue shaded areas in the polar regions represent the sea ice maximum from the climatological period (1993-2022). Monitoring SST extremes with the MHW categorization approach as used here is not best suited for such regions.

 

 

  • 27% of the surface of the ocean was impacted by strong-or-higher MHW conditions for at least 1 day during July 2026. This is the 1st widest extent of the last 34 years, far exceeding the previous record set in 2024 (22 %). The central Pacific and the Southern Ocean, between 40°E and 80°E are the most affected, with areas where MHWs persisted the entire month. In the south of New Zealand and south of the Bering Sea, MHWs also persisted throughout the month.
 MHW days of strong and higher category in July 2026 in the Equatorial Pacific (30°S-30°N).

 

Year by year evolution of the surface impacted by strong and higher MHW during months of July. The size of the bar represents the proportion of the global ocean (between 60°S and 60°N) exposed to a strong or higher MHW during the month. As indicated by the colours, the proportion exposed to such MHWs is categorized according to the number of days impacted during the month.

 

 

  • Regionally, 31% of the North Atlantic (between 0°N and 60°N) was impacted by strong, or higher, MHW conditions for at least 1 day. This corresponds to the 3rd largest extent of the last 34 years for a July month, behind 2024 (48%) and 2023 (55%). Western Europe and the band between 25°N and 35°N are the regions that have been affected by strong MHWs or higher for the longest period of time

 

Year by year evolution of the surface impacted by strong and higher MHW during months of July. The size of the bar represents the proportion of the North Atlantic (0°N- 60°N) exposed to a strong or higher MHW during the month. As indicated by the colours, the proportion exposed to such MHWs is categorized according to the number of days impacted during the month.

 

  • In the Mediterranean Sea, 79% of the basin was affected by strong-or-higher MHW conditions for at least 1 day, which is a record for the month of July, far ahead of July 2025 with 70%.

 

Year by year evolution of the surface impacted by strong and higher MHW during months of July. The size of the bar represents the proportion of the Mediterranean Sea, exposed to a strong or higher MHW during the month. As indicated by the colours, the proportion exposed to such MHWs is categorized according to the number of days impacted during the month.

 

Statistics

Marine heatwave duration, intensity, extent and activity

  • On a global scale, July 2026 was the most extreme July in terms of MHW, well ahead of 2023 and 2024
  • In the Mediterranean Sea, July 2026 was the most extreme July in terms of MHW mean duration, and the 2nd in terms of MHW mean intensity, behind 2025.
  • In the North Atlantic, July 2026 was the 3rd most extreme July month in terms of MHW from the last 34 years, behind 2024 and 2023.

 

MHW characteristics for july months from 1993 to 2026. Duration, intensity, extent and activity averaged for each July month between 1993 and 2026 for the global ocean (top), for the Mediterranean Sea (centre) and the North Atlantic Ocean (bottom). July 2026 is highlighted with a blue edge.

 

About the Bulletin

Mercator Ocean International publishes a monthly sea surface temperature bulletin reporting on mean temperature and marine heatwave conditions for the month just passed. It includes:

  • Regions where MHWs are present and the time these events started,
  • Timeseries showing the total surface occupied by MHWs globally and for the European region,
  • The total number of days of exposure to MHW during the month (including only strong and higher intensity categories).

Data sets and products

Sea Surface Temperature

The results are obtained using the Copernicus Marine Service global analysis and forecasting system together with observation-based products.

  • GLOBAL_ANALYSISFORECAST_PHY_001_024 Global Ocean Physics Analysis and Forecast sea surface temperature. U. Copernicus Marine Service Information (CMEMS). Marine Data Store (MDS). DOI: https://doi.org/10.48670/moi-00016
  • ESA SST CCI reprocessed sea surface temperature analyses. E.U. Copernicus Marine Service Information (CMEMS). Marine Data Store (MDS). DOI: https://doi.org/10.48670/moi-00169
  • NOAA OI SST V2 High Resolution Dataset data provided by the NOAA PSL, Boulder, Colorado, USA, from their website at https://psl.noaa.gov, Huang, B., C. Liu, V. Banzon, E. Freeman, G. Graham, B. Hankins, T. Smith, and H.-M. Zhang, 2021: Improvements of the Daily Optimum Interpolation Sea Surface Temperature (DOISST) Version 2.1, Journal of Climate, 34, 2923-2939. doi: 10.1175/JCLI-D-20-0166.1
  • Global Ocean OSTIA Sea Surface Temperature and Sea Ice Analysis. E.U. Copernicus Marine Service Information (CMEMS). Marine Data Store (MDS). DOI: https://doi.org/10.48670/moi-00165
  • ODYSSEA Global Sea Surface Temperature Gridded Level 4 Daily Multi-Sensor Observations. E.U. Copernicus Marine Service Information (CMEMS). Marine Data Store (MDS). DOI: https://doi.org/10.48670/moi-00016

Notes: The global analysis system was used to study the ocean surface temperature from 2021 and 2025. To study surface temperature for previous years (1991 to 2020), it was used the ESA CCI data. The other observation-based sea surface temperature products (OSTIA, OI SST and Odyssea) were used for calculating monthly mean and uncertainty values for July 2026.

 Marine Heatwaves

The results are obtained using the Copernicus Marine Service global systems including the analysis and forecasting system together with the reanalysis product.

  • GLOBAL_ANALYSISFORECAST_PHY_001_024 Global Ocean Physics Analysis and Forecast sea surface temperature. U. Copernicus Marine Service Information (CMEMS). Marine Data Store (MDS). DOI: https://doi.org/10.48670/moi-00016
  • GLOBAL_MULTIYEAR_PHY_001_030 Global Ocean Physics Reanalysis sea surface temperature. U. Copernicus Marine Service Information (CMEMS). Marine Data Store (MDS). DOI: https://doi.org/10.48670/moi-00021

Notes: The global analysis system was used to study MHWs for 2024 and 2025. To study MHWs for previous Julys (1993 to 2025), it was used the reanalysis system. The reanalysis product was used for generating a daily climatology using the 30-year period from 1993 to 2022