Flash Flood Warnings Cover New York City Boroughs and New Jersey as South Korea Sets Heat Records

The National Weather Service has issued multiple flash flood warnings for parts of New Jersey, Pennsylvania and the New York City metro area as thunderstorms produce heavy rain, while South Korea grapples with a record-breaking heat wave that has triggered the country's first highest-level heat emergency warning for the greater Seoul area.

Flash Flood Warnings Issued Across New Jersey and New York Metro

Flash Flood Warnings remain in effect for southeastern Essex County, Hudson County, eastern Union County in New Jersey, and multiple New York City boroughs and counties including the Bronx, Brooklyn, Manhattan, Queens, Staten Island, and western Nassau County. [1] A separate Flash Flood Warning covering northwestern Mercer County, Morris County, Somerset County and southeastern Hunterdon County in New Jersey was extended until 7:15 a.m. EDT after Doppler radar showed thunderstorms producing heavy rain, with gauges on the Whippany River recording significant rises. [2] The National Weather Service in Upton issued the warning that covers southeastern Essex County in northeastern New Jersey, Hudson County in northeastern New Jersey, eastern Union County in northeastern New Jersey, Bronx County in southeastern New York, Kings (Brooklyn) County in southeastern New York, western Nassau County in southeastern New York, New York (Manhattan) County in southeastern New York, Queens County in southeastern New York and Richmond (Staten Island) County in southeastern New York. [1] The National Weather Service in Mount Holly extended the warning for northwestern Mercer County in central New Jersey, Morris County in northern New Jersey, Somerset County in northern New Jersey and southeastern Hunterdon County in northwestern New Jersey until 7:15 a.m. EDT. [2] At 5:37 a.m. EDT, Doppler radar and automated rain gauges indicated thunderstorms producing heavy rain across portions of the warned area, and gauges on the Whippany River at Morristown recorded significant rises. [2]

Heavy Rain Triggers Flooding in Pennsylvania

In Bucks County, Pennsylvania, between 1.5 and 3 inches of rain fell in a short period, causing ongoing flash flooding of small creeks, streams, urban areas, highways, streets and underpasses. [5] At 5:09 a.m. EDT, Doppler radar and automated rain gauges indicated thunderstorms producing heavy rain across the warned area in Bucks County. [5] Between 1.5 and 3 inches of rain have fallen, and flooding impacts will continue even though no additional rainfall is expected. [5] Flash flooding is ongoing or expected to begin shortly in the area. [5] The hazard consists of flash flooding caused by thunderstorms, with the source identified as radar and automated gauges. [5] The impact includes flooding of small creeks and streams, urban areas, highways, streets, and underpasses as well as other drainage areas. [5]

South Korea Swelters Under Record Heat Wave

South Korea recorded a new high of 41.2 C in Goryeong County and 40.9 C in Daegu on Monday, with Yangsan reaching 42.5 C on Sunday; the extreme heat has caused at least three heat-related deaths. [3] Temperatures reached a record high of 40.9 C in the southeastern city of Daegu, surpassing the 40 C mark for the first time since Aug. 1, 1942. [3] Goryeong County, about 230 kilometers southeast of Seoul, reported the nation's highest temperature of the day at 41.2 C at 3:37 p.m. [3] In the southeastern city of Yangsan, where temperatures reached the highest recorded temperature of 42.5 C on Sunday since modern weather observations began in 1904, temperatures peaked at 38 C. [3] The extreme heat has triggered health emergencies across the country. [3] In Incheon, west of Seoul, a man in his 40s died Monday morning with his bodily temperature nearing 40 C after being sent to a hospital the previous day. [3] Also on Sunday, two farmers, in their 60s and 80s, respectively, were found dead in the central province of South Chungcheong. [3]

Highest-Level Heat Emergency Warning for Seoul Region

The Korea Meteorological Administration issued its highest-level Heat Wave Emergency Warning for southern Seoul districts, parts of Gyeonggi Province and additional counties, the first time for the greater Seoul area, due to forecast highs exceeding 39 C and perceived temperatures over 38 C. [3][4] The Korea Meteorological Administration issued the warning at 4 p.m. for Tuesday, when the daily maximum perceived temperature is expected to exceed 38 degrees Celsius and the daytime high is forecast to surpass 39 C. [4] The warning, the highest level in the KMA’s heat alert system, applies to all Seoul districts south of the Han River, including Gangnam-gu, as well as Osan, Hanam and western Yeoju in Gyeonggi Province. [4] Under the warning, authorities strongly recommend suspending nonessential outdoor work and moving to air-conditioned indoor spaces or cooling shelters. [4] They also advise stepped-up safety checks on vulnerable households. [4] The highest-level warning had previously been issued mainly in southeastern areas, particularly South Gyeongsang Province, after Yangsan recorded a national high of 42.5 C on Sunday. [4]

Meteorological Causes and Outlook

The KMA attributed the prolonged high temperatures to overlapping high-pressure systems over the peninsula combined with strong, direct sunlight under clear skies. [3] The KMA attributed the westward spread of the heat to easterly winds carrying hot air toward the capital region. [4] High temperatures are also expected to persist overnight and in the coming days. [4] As heat accumulated during the day continues into the night, residents in the metropolitan area are urged to regularly check the latest weather information and take extra precautions, including staying hydrated and getting sufficient rest. [4] Severe heat wave warnings remained in effect across southwestern parts of the country, with one of the criteria for the warning being a high of at least 38 C in perceived temperature for more than a day. [3] The KMA said additional severe heat wave warnings will take effect at 11 a.m. Tuesday in southern Seoul, parts of Gyeonggi Province surrounding the capital, as well as Jangseong and Gokseong counties in South Jeolla Province. [3]

What to watch next: The National Weather Service warnings in New Jersey and New York remain active with ongoing radar monitoring of heavy rain, while the Korea Meteorological Administration’s Heat Wave Emergency Warning for the greater Seoul area takes effect Tuesday with expected highs above 39 C and perceived temperatures over 38 C.