"Heat Dome" Phenomenon Occurs in the U.S.! Feels Like Over 43°C in NY, 160 Million People Under Heat Warning - Once-in-a-Decade Scorching Heat Arrives

2025年06月27日 21:45

Introduction
What is a Heat Dome?
Scale of the Current Heatwave
From the Scene in New York
Health Impacts and Vulnerable Populations
Impact on Social Infrastructure
Relation to Climate Change
Implications for Japan
Summary and Outlook

1. Introduction

In late June, a heat dome covering a wide area of the United States prompted the NWS (National Weather Service) to issue heat warnings to approximately 160 million people across 28 states. In New York City, the heat index reached 43°C, with temperatures exceeding 40°C in Boston and Philadelphia, being described as a "once-in-a-decade heatwave"reuters.comhindustantimes.com.

2. What is a Heat Dome?

A heat dome is a phenomenon where a strong high-pressure system in the upper atmosphere acts as a "lid," trapping heat near the surface. This makes cloud development difficult and inhibits radiative cooling at night, leading to prolonged high temperatures and persistently high humidity. When factors like ENSO and jet stream blocking are added, the scale can easily expand, and studies suggest that climate change could triple the frequency of such events.

3. Scale of the Current Heatwave

The high-pressure system that settled over the Midwest around June 20 expanded to the East Coast within a few days. The NWS declared "extreme heat," leading to a state of emergency in 32 counties in New York State. Central Park recorded 37.8°C, matching records from 1888, with a heat index of 43°Creuters.com. About half of the total population was placed in a danger zone, with media outlets reporting that "over 160 million people are under alert"hindustantimes.com.

4. From the Scene in New York

The Metropolitan Transportation Authority (MTA) imposed speed restrictions to counter rail expansion, and Amtrak also reduced its speed. The impact was widespread, including mandatory air conditioning inspections at polling stations and the closure of the Washington Monument. The city opened over 700 cooling centers and encouraged evacuation for the homeless and elderly. Emergency transports increased to about 1.8 times the usual rate, with reports of ICU patient transfers in hospitals.

5. Health Impacts and Vulnerable Populations

According to CDC statistics, heat-related deaths in the U.S. are around 700 annually. This time, heatstroke was prevalent, particularly among outdoor workers and the elderly, with a construction worker's death reported in New Hampshire. The WBGT exceeded 35°C, the "lethal zone," in multiple cities for consecutive days, far surpassing WHO standards.

6. Impact on Social Infrastructure

Peak electricity demand increased by 15%, prompting NYISO to issue an emergency supply-demand declaration, and Boston and Chicago implemented an 8% voltage reduction. Highways were closed due to road softening, and agriculture faced yield risks as corn and soybeans experienced heat stress during flowering. Fuel costs for refrigerated trucks rose, impacting logistics prices.

7. Relation to Climate Change

The IPCC's Sixth Assessment Report warns of the "annualization of extreme heat," and this case is an example. It is analyzed that the overlap of La Niña and the North Atlantic High caused the heat dome to stagnate. If greenhouse gas emissions continue, the likelihood of annual heat domes in North America by the mid-21st century increases.

8. Implications for Japan

In Japan, the number of days with temperatures exceeding 40°C is increasing, with heatstroke deaths reaching about 1,000 annually since 2023. The rise in nighttime urban temperatures combined with an aging population is making a "silent disaster" similar to the U.S. a reality. Comprehensive "heat resilience" measures, such as mandatory cool roofs on buildings, urban greening, compensation for outdoor work breaks, air conditioning installation support, and the development of DER and supply-demand adjustment markets, are urgently needed.

9. Summary and Outlook

The recent U.S. heat dome has become a typical example of how the climate crisis shakes daily life and economic activities. Countries, including Japan, need to accelerate both mitigation (GHG reduction) and adaptation (strengthening society and infrastructure). Early warning through satellite data and AI, peak shifting via V2G, and a network of regional cooling centers will be key in a multi-layered approach.