Marek Kučera 
Hong Kong has shattered its historical temperature records by soaring to an unprecedented +38.9°C, marking the hottest June day ever recorded in the city’s meteorological history. This remarkable heat event underscores the increasing intensity of extreme weather in the region amid ongoing climate change.
Meteorological Analysis
Hong Kong’s climate is typically characterized by hot, humid summers moderated by the surrounding South China Sea. However, this year’s extreme temperature surge was driven by a convergence of atmospheric factors:
- A strong subtropical high-pressure system (Western Pacific Subtropical High) expanded westward, creating a persistent heat dome over southern China.
- Under this high-pressure ridge, subsidence (sinking air) led to clear skies and suppressed convective clouds, allowing solar radiation to reach the surface unobstructed.
- Offshore winds weakened, reducing the usual cooling sea breezes that typically moderate daytime temperatures in Hong Kong’s coastal urban environment.
- Elevated humidity levels combined with soaring temperatures have led to extreme heat stress conditions, with heat index values significantly exceeding the actual air temperature.
Climatological Context
Historically, June temperatures in Hong Kong average between 28°C and 33°C, with occasional spikes into the mid-30s during heatwaves. Prior to 2025, the previous highest June temperature was recorded at 38.3°C. The new record of +38.9°C exceeds that by 0.6°C, a substantial margin in a region where temperatures rarely reach such extremes.
This event fits into a broader pattern of increasing heat extremes observed across East Asia. The region has seen more frequent and intense heatwaves in recent years, partly driven by anthropogenic climate change and local urban heat island effects.
Impacts and Response
The record-breaking heat poses significant risks to public health, infrastructure, and energy systems in Hong Kong:
- Heat-related illnesses such as heat exhaustion and heat stroke have surged, particularly among vulnerable populations including the elderly and outdoor workers.
- The demand for electricity to power air conditioning units has reached new highs, straining the power grid.
- Transport infrastructure, including rail and road surfaces, has faced challenges due to thermal expansion and heat stress.
The Hong Kong Observatory issued extreme heat warnings, advising residents to stay hydrated, avoid strenuous outdoor activities during peak heat hours, and check on neighbors who might be at risk.
Forecast Outlook
Numerical weather models indicate that the subtropical ridge will persist for several more days, maintaining elevated temperatures. Slight relief may come later in the week with the approach of a weak trough, bringing isolated showers and somewhat lower temperatures.
Summary
Hong Kong’s record-setting temperature of +38.9°C in June 2025 is a clear indicator of shifting climate patterns and increasing heat extremes in the region. This historic heat underscores the urgency of climate adaptation strategies and enhanced public health preparedness to cope with the rising frequency of such events.
Illustration picture: https://www.scmp.com/yp/discover/advice/personal-development/article/3068590/best-spots-hong-kong-catch-first-sunrise
