September 2025 marked the world's third warmest September on record, as announced by the EU's Copernicus Climate Change Service (C3S). Land and sea surface temperatures remained significantly elevated, reflecting the ongoing impact of greenhouse gas accumulation.

• The global average surface temperature in September 2025 was 16.11 degrees Celsius, which is 1.47 degrees above pre-industrial levels.
• Samantha Burgess, strategic lead for climate in the C3S, highlighted that this September was less than 0.1 degrees Celsius cooler than September 2024.
• Global average sea surface temperature reached 20.72 degrees Celsius, also ranking as the third highest for the month, with significant warming in the North Pacific.