October 2023 was the warmest October globally in the ERA5 data record, going back to 1940, according to the latest monthly climate update from the Copernicus Climate Change Service (C3S). The average surface air temperature reached 15.30°C, 0.85°C above the 1991-2020 average for October. This marks the second highest global temperature anomaly across all months in the ERA5 dataset, after September 2023 (with an anomaly of 0.93°C). October 2023 was 1.7°C above the average for 1850-1900, designated as the pre-industrial reference period.
https://climate.copernicus.eu/2023-track-become-warmest-year-after-record-october