September was the warmest September on record according to the latest data from the Copernicus Climate Change Service (C3S), implemented by the European Centre for Medium-Range Weather Forecasts on behalf of the European Commission.

It routinely publishes monthly climate bulletins reporting on the changes observed in global surface air temperature, sea ice cover and hydrological variables.

All the reported findings are based on computer-generated analyses using billions of measurements from satellites, ships, aircraft and weather stations around the world.

September climate data

In terms of surface air temperature and sea surface temperature the latest report states that September 2023 was the warmest September on record globally, with an average surface air temperature of 16.38°C.

This was 0.93°C above the 1991-2020 average for September and 0.5°C above the temperature of the previous warmest September, in 2020.

The month as a whole was around 1.75°C warmer than the September average for 1850-1900, the pre-industrial reference period.

The global temperature for January-September 2023 was 0.52°C higher than average, and 0.05°C higher than the equivalent period in the warmest calendar year (2016).

Source: Copernicus Climate Change Service

For January to September 2023, the global mean temperature for 2023 to date is 1.40°C higher than the preindustrial average (1850-1900). 

For Europe, September 2023 was the warmest September on record, at 2.51°C higher than the 1991-2020 average, and 1.1°C higher than 2020, the previous warmest September.  

The average sea surface temperature for September reached 20.92°C, the highest on record for September and the second highest across all months, behind August 2023.

El Nino conditions continued to develop over the equatorial eastern Pacific.

Samantha Burgess, deputy director of the Copernicus Climate Change Service (C3S) said: “The unprecedented temperatures for the time of year observed in September – following a record summer – have broken records by an extraordinary amount.

“This extreme month has pushed 2023 into the dubious honour of first place – on track to be the warmest year and around 1.4°C above pre-industrial average temperatures.

“Two months out from COP28 – the sense of urgency for ambitious climate action has never been more critical.”

September 2023 also saw wetter-than-average conditions along many parts of the western seaboard of Europe, including Ireland, the western Iberian Peninsula, northern Britain, and Scandinavia.

It was also wetter than average in Greece following extreme rainfall associated with storm Daniel; this event was also responsible for the devastating flooding in Libya, the report states.

Southern Brazil and southern Chile also experienced extreme precipitation events. 

Drier-than-average regions included parts of Europe, the south-eastern US, Mexico, central Asia, and Australia, where the driest September on record was recorded.