The first of multiple Arctic blasts expected this month brought record-low temperatures across the Midwest on Thursday, December 4, 2025, with reports of over 40 record lows for the day. More record lows are expected as the Arctic wave moves through the Northeast on Friday, December 5.
Low-level eruptive activity resumed at Ambae volcano (Manaro Voui) in Vanuatu, with intermittent ash emissions observed since December 1, 2025. Satellite imagery from Himawari-9 confirmed continuous low-level ash and gas plumes reaching up to 1.8 km (6 000 feet) above sea level, drifting northwest. The Wellington Volcanic Ash Advisory Centre (VAAC) issued its latest advisory on December 4, describing the eruption as continuous but confined within the volcano’s summit area.
Multiple winter weather advisories are in effect across Texas and the Oklahoma panhandles on Thursday morning, December 4, 2025, as snow and sleet create hazardous travel conditions through early afternoon.
Heavy snow squalls are forecast to hit much of the U.S. Northeast through Thursday, December 4, 2025, with New York State and parts of New England expected to see the strongest impact. The snow squalls triggered by, and arctic surge will create dangerous travel conditions across key routes including the I-90 corridor.
Three atmospheric rivers (ARs) are forecast to make landfall over the Pacific Northwest (PNW) through December 10, 2025, producing prolonged precipitation and high moisture transport across western Washington and Oregon.
A shallow earthquake registered by the USGS as M5.8 struck southern Xinjiang, China at 07:44 UTC (13:44 local time) on December 4, 2025. The agency is reporting a depth of 10 km (6.2 miles). The USGS issued a Green alert for shaking-related fatalities and a Yellow alert for economic losses.
New activity/unrest was reported for 9 volcanoes from November 26 to December 2, 2025. During the same period, ongoing activity was reported for 20 volcanoes.
The polar vortex is forecast to settle near Hudson Bay, sending repeated waves of Arctic air into the central and eastern U.S. during the first half of December 2025.
Volcanic activity at Puracé, Colombia, intensified on November 30, 2025, prompting authorities to raise the alert level to Orange for the Los Coconucos volcanic chain in Cauca Department on December 1. Since then, continuous tremor, long-period seismicity, and sustained gas-and-ash emissions have been recorded, with columns exceeding 700 m (2 300 feet) above the summit (4 650 m / 15 260 a.s.l.) and occasional ashfall reported in nearby communities.
Downtown San Francisco reached only 10°C (50°F) on Sunday, November 30, 2025 – the city’s lowest daily maximum for the date in records dating back to 1874. The unseasonably cold conditions developed under a persistent marine layer and stagnant air pattern, keeping the city unusually cold for late autumn.
