January 2025 was the warmest January globally, with an average ERA5 surface air temperature of 13.23°C, 0.79°C above the 1991-2020 average for January.
January 2025 was 1.75°C above the pre-industrial level and was the 18th month in the last nineteen months for which the global-average surface air temperature was more than 1.5°C above the pre-industrial level.
The last 12-months period (February 2024 – January 2025) was 0.73°C above the 1991-2020 average, and 1.61°C above the estimated 1850-1900 average used to define the pre-industrial level.

According to Samantha Burgess, Strategic Lead for Climate at ECMWF:

"January 2025 is another surprising month, continuing the record temperatures observed throughout the last two years, despite the development of La Niña conditions in the tropical Pacific and their temporary cooling effect on global temperatures. Copernicus will continue to closely monitor ocean temperatures and their influence on our evolving climate throughout 2025.”

https://climate.copernicus.eu/copernicus-january-2025-was-warmest-record-globally-despite-emerging-la-nina

Climate scientists had expected this exceptional spell to subside after a warming El Nino event peaked in January 2024 and conditions gradually shifted to an opposing, cooling La Nina phase.

But the heat has lingered at record or near record levels ever since, sparking debate among scientists about what other factors could be driving heating to the top end of expectations.

"This is what makes it a bit of a surprise... you're not seeing this cooling effect, or temporary brake at least, on the global temperature that we were expecting to see," Julien Nicolas, a climate scientist from Copernicus, told AFP.

La Nina is expected to be weak and Copernicus said prevailing temperatures in parts of the equatorial Pacific Ocean suggested "a slowing or stalling of the move towards" the cooling phenomenon.

https://www.france24.com/en/europe/20250206-january-heat-la-nina