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Seasonal / UV-Index Topics

January 2025 Was the Hottest January on Record — Even With La Niña

Record warmth during a 'cooling' La Niña is a reminder that winter is no longer a season to skip SPF.

By the numbers

Copernicus reported January 2025 as the warmest January on record globally at 1.75°C above pre-industrial levels — the 18th of the last 19 months above the 1.5°C threshold — despite emerging La Niña conditions.

Climate scientists at Copernicus highlight that reaching a record-warm January even as La Niña began to cool the Pacific underscores how dominant the long-term warming signal has become.
What the evidence actually says — Copernicus: January 2025 warmest on record despite emerging La Niña

Questions we get a lot

How hot was January 2025?

According to the Copernicus Climate Change Service, January 2025 was the warmest January on record globally, at 1.75°C above the pre-industrial baseline. It was the 18th month out of the last 19 to exceed 1.5°C above pre-industrial levels.

Why is a record warm January significant if La Niña was forming?

La Niña typically exerts a cooling influence on global temperatures, so setting a record while it emerged shows how strong the underlying warming trend has become. It suggests heat and high-UV conditions are increasingly persistent rather than seasonal.

Should I still wear sunscreen in winter?

Yes. UV radiation reaches the skin year-round, and persistently warmer conditions mean longer stretches of elevated exposure. Dermatologists recommend daily broad-spectrum SPF regardless of season, since UVA in particular passes through clouds and windows.

What people keep asking

r/SkincareAddiction: 'Do I really need to wear sunscreen in winter, or is that overkill?'

Sources & citations

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