🔥 June 2025: A Scorching New Benchmark

Earliest onset of summer-like heat: Typically, the hottest consecutive five-week period starts around July 10. In 2025, this heat wave began as early as June 13, extending through early September—echoing patterns from 2023.

Regions across the Northern Hemisphere—including Canada, the northeastern U.S., northern Europe, China, Pakistan, and northern India—experienced exceptionally high temperatures, with several places recording or tying local June records .

🌡️ Heat Domes and Record Temperatures

Strong heat domes—static high-pressure systems trapping hot air—affected the Central & Eastern U.S. and Europe, pushing temperatures past 40 °C (104 °F). In the U.S., NYC’s JFK hit 40 °C+, Central Park nearly touched 38 °C, Boston topped 39 °C, and Newark recorded its hottest June day at 41 °C .

In Canada, Greece, Spain, France, and Portugal, many cities hit perilous June peaks: up to 42 °C in Spain and over 40 °C in Portugal

📉 Human Influence: Climate Change’s Fingerprint

These extreme heat events now occur three times more often than they did in pre-industrial times, thanks to greenhouse gas-driven warming 

One study quantified that nearly half of the U.S. population (around 174 million) faced heat events made at least three times more likely by climate change

In the UK, a June heatwave was found to be 100× more probable due to human warming; experts forecast that at 2–4 °C hotter, such heatwaves are increasingly lethal, contributing to tens of thousands of premature deaths .

🧭 ENSO-Neutral, but Temperatures Soar

Despite expectations of ENSO-neutral conditions (meaning neither El Niño nor La Niña), June saw record-setting warmth. The usual ENSO-driven variability played little part—global warming remains the dominant driver 

⚠️ Top-Level Takeaways

🌍 What’s Next?

Expect longer, earlier summers, more frequent heat domes, and rising stress on energy, healthcare, and ecosystems.

Urgent actions are needed: prioritize cooling infrastructure, early warning systems, and greenhouse gas reduction to avoid repeated June crises.