Forecast data indicate an early weakening and displacement of the stratospheric polar vortex over the Arctic in October 2025, as a developing high-pressure anomaly over Greenland interacts with the circulation earlier than usual, increasing the chances of colder air movement toward the mid-latitudes of North America and Europe.
A secondary lahar flow originating from remobilized pyroclastic and tephra deposits on the southern flank of Mount Semeru, Indonesia, occurred on October 21, 2025, trapping a truck near Gladak Perak Bridge in Lumajang Regency, East Java. The rain-induced lahar, classified as a cold, non-eruptive sediment-water flow, moved through the Besuk Kobokan drainage, carrying a dense slurry of volcanic debris and runoff.
A low-pressure area in the Caribbean Sea, designated AL98, is forecast to develop into the 13th named storm of the 2025 Atlantic hurricane season, “Melissa,” later on October 21, 2025, with a 100% probability of cyclonic development within the next 48 hours.
The Pacific Northwest will see back-to-back atmospheric rivers (ARs) beginning late Thursday, October 23, 2025, bringing significant precipitation and unsettled weather conditions through the end of October.The Weather Prediction Center has issued a Marginal Risk of excessive rainfall for coastal areas of Washington, Oregon, and northern California as the AR approaches.
Air quality across New Delhi, India, deteriorated sharply between October 19 and 21, 2025, reaching “very poor” and “severe” levels at multiple monitoring stations. According to the Central Pollution Control Board (CPCB), the 24-hour average AQI rose from 296 on October 19 to 345–346 on October 20–21, prompting Stage II measures of the Graded Response Action Plan (GRAP) across the National Capital Region.
A deadly tornado struck the Val-d’Oise department, north-east of Paris, France, at around 17:45 LT (15:45 UTC) on October 20, 2025, killing one person and injuring nine, four critically. The violent, short-lived storm collapsed several construction cranes in Ermont, caused widespread roof damage, and uprooted trees across neighbouring municipalities.
A strong seismic swarm began beneath Iceland’s Mýrdalsjökull glacier, part of the Katla volcanic system, around 10:30 UTC on October 20, 2025. Several earthquakes above magnitude 3 were recorded, the largest reaching M4.5 at 10:51 UTC. The Icelandic Meteorological Office reports no felt activity and no changes in river levels, conductivity, or deformation, indicating no immediate signs of eruption at the Katla volcano or glacial flooding.
New Zealand is set for a week of active weather as multiple systems track across the country from October 20 to 23, 2025. MetService warns of strong northwesterlies and heavy rain early in the week, followed by another intense front on Thursday that may bring more severe impacts to already affected areas.
Strong winds and very low humidity prompted the National Weather Service to issue a Red Flag Warning across Colorado’s Front Range on October 20 2025, creating critical fire-weather conditions and an increased risk of power disruptions. Xcel Energy warned customers in the Denver metropolitan area of potential outages and activated Enhanced Powerline Safety Settings (EPSS), which increase system sensitivity to prevent wildfire ignition during extreme weather.
Tropical Storm Fengshen (locally named Ramil in the Philippines) crossed Luzon on October 18 and 19, 2025, producing torrential rain, flooding, and landslides. At least five people were killed in Quezon Province, while two others remain missing in Bukidnon after a landslide.
