Thanks to La Niña conditions – the periodic cooling of the tropical Pacific Ocean that has a cooling effect on the global average temperature – the global average temperature was not very high from December to February. Each of the three months from December 2025 to February 2026 ranked fifth warmest. This relatively cool period is now coming to an end, HT’s analysis of temperature data for March and April indicates. This is because the effect of “La Niña” conditions is now fading.
That the recent months of December, January and February ranked as the fifth warmest does not, under normal circumstances, indicate cold weather. But it likely appeared colder than the months of December, January and February that immediately preceded it. That’s because every month from June 2023 to November 2025 so far has ranked in the top three warmest on record.
However, the three-month spell of cold weather ended in March, which ranked as the fourth warmest month in March, according to the ERA5 dataset published by the European Center for Medium-Range Weather Forecasts (ECMWF). This is also the case for April so far. The first 25 days of April this year ranked as the fourth warmest in the ERA5 data.
Granted, even though April ranks in the same league as March, there has been a shift in April compared to March. As the accompanying chart shows, March 2026 was 0.09°C colder than the third month in March (recorded in 2016). On the other hand, April 2026 is much closer to the third-ranking April (also recorded in 2016): only 0.01°C cooler.
Chart 1
In fact, it’s possible that by the time the month is over, April 2026 will rank as the third warmest April. This is because April 2016 was overall 1.44°C warmer than the pre-industrial average, while April 2026 so far is 1.45°C warmer than the pre-industrial average. This means that the remaining five days of April need an average deviation of 1.38°C from the pre-industrial average for April 2026 to be tied to April 2016. This average level of warming is within the range of possible given the trends in the past week.
Chart 2
Why is global warming rising relative to the pre-industrial average again? One possible reason is that the effect of La Niña is beginning to fade.
La Niña conditions are tracked by measuring the average deviation of sea surface temperatures (SST) in the 5N-5S region, 170W-120W (Nino 3.4 region) from the 30-year average. When this region shows a negative deviation of 0.5°C or more, La Niña conditions are said to exist. When the region shows a positive deviation of 0.5°C or more, La Niña conditions are said to exist, which has the opposite effect of La Niña, which is a warming of the global average temperature. When the deviation is less than 0.5°C, neutral conditions are said to exist.
Data indicate that the Nino 3.4 region entered neutral conditions at the end of January. This did not lead to an immediate rise in air temperatures because it takes time – about two to four months – for changes in sea surface temperatures to affect air temperatures. Temperature data for April indicate that the ongoing influence of La Nina is now coming to an end.
Chart 3
Certainly, the latest El Nino 3.4 temperature data shows that even neutral conditions are likely over. El Niño conditions were in place for the two weeks ending April 22. If these conditions persist, El Niño could occur a month earlier than expected in early April forecasts. This could mean new record temperatures in June.
