🌎 Weekly Global Weather Watch

Heat grips two hemispheres, Tokyo drowns in a day’s worth of rain, and the tropics stir on both oceans

DATELINE: WEEK OF AUGUST 11–17, 2026 — It has been a week of extremes pulling in opposite directions across the globe. A stubborn heat dome parked over Central Europe and the Balkans pushed temperatures past 40°C for the fifth time this summer, while the U.S. Southwest notched another August heat record in Phoenix. At the same time, a slow-moving deluge over Chiba, Japan, dumped three times a normal August’s worth of rain in half a day, killing at least eight people and stranding tens of thousands during the Obon holiday travel rush. Winter arrived hard in the Southern Hemisphere, with rare snow blanketing Gauteng, South Africa, and a potentially season-saving cold front burying the Australian Alps. Meanwhile, the Atlantic’s first serious tropical threat of the year is organizing off Africa, and the jet stream’s split personality — a heat-trapping ridge over the U.S. South and Southwest paired with an unusually active trough diving into the eastern Pacific — is setting the stage for an early-season pulse of West Coast rain. Here is what’s driving the weather worldwide this week, and what to watch as the pattern evolves.

Major weather systems developing

The dominant story this week is a tale of blocking highs versus restless troughs. Over Europe, a broad upper-level ridge — described by forecasters as acting “like a lid on a pot” — has locked in an Omega blocking pattern that has repeatedly regenerated heat domes over the continent since mid-July, with the current one expanding eastward toward Ukraine and western Russia by week’s end. Across the Atlantic, the U.S. is caught between a strengthening ridge centered over the Southwest and southern Plains and a series of shortwave troughs digging into the East, a setup the NOAA Weather Prediction Center says will keep firing off rounds of thunderstorms from the Mississippi Valley to the Eastern Seaboard through the weekend. In the tropics, Invest 92L — a vigorous disturbance roughly 500 miles southwest of the Cabo Verde Islands — carries a 70 percent chance of developing into the Atlantic’s next depression within days, while in the Southern Hemisphere a deep cut-off low and reinforcing cold fronts have driven an unusually intense mid-winter cold snap across South Africa and southeastern Australia.

Heat waves

Europe is enduring its fifth heat wave of the summer, an event forecasters say is “lasting longer than the deadly heat wave of 2003” and is currently affecting roughly 300 million people — more than half the continent’s population. France logged 21 monthly temperature records on August 12, topping out at 105.6°F (40.9°C) in Beaulieu-sur-Layon, while London’s Kew Gardens hit 100°F for one of its five hottest days on record and southern England touched the century mark for the first time this summer, igniting wildfires in the New Forest and West Midlands. Wales may have recorded its hottest day ever at 95.5°F. Peak heat-dome temperatures of 40–43°C are forecast across the Pannonian and Po Valley plains, with overnight lows stuck at a punishing 22–26°C — so-called “tropical nights” that deny residents any recovery — and France has declared a “historic and critical” drought across nearly 70 percent of the country, forcing Romania to idle nuclear reactors on the low Danube. On the other side of the globe, the U.S. Southwest has been locked in a parallel siege: Phoenix hit 118°F on August 13, tying for the ninth-hottest day in Arizona records dating to 1895, while heat advisories and warnings stretch from Palm Springs and Tucson through Albuquerque, Dallas, Oklahoma City, Denver and into the Plains, with heat indices as high as 105–115°F and record-warm overnight lows compounding the strain.

Cold outbreaks

With the Southern Hemisphere in the depths of winter, a deep cold snap has swept across southern Africa and southeastern Australia this week. A cut-off low and reinforcing cold front brought rare, disruptive snowfall to three South African provinces, including Gauteng — with snow reported in Johannesburg South, Oakdene and the East Rand, plus heavier totals in the Drakensberg — alongside damaging winds and at least one weather-related death. In Australia, a cold front that arrived August 9 delivered the most significant snowfall of the 2026 ski season, with more than 50 centimeters possible at the highest elevations of the Australian Alps and snow levels dropping to roughly 1,000 meters, low enough to blanket Perisher, Thredbo and Mount Hotham at base level. The storm offered welcome relief to a historically bad season: before its arrival, the benchmark Spencers Creek snow course had measured just 34.3 inches, barely above the all-time record low set in 2006, the result of a positive Southern Annular Mode and El Niño-related patterns that have steered storms away from the continent for much of the season.

Flood threats

The week’s most devastating flooding struck the Tokyo metropolitan area on August 14, when record-breaking rainfall over Chiba Prefecture delivered roughly three times the region’s normal August monthly total in just half a day. At least eight people were killed, more than 100,000 residents were evacuated, about 40 percent of Japan’s prefectures reported flooding impacts, and over 20,000 households lost power as the storm snarled Obon holiday travel, stranding thousands at Narita International Airport and shutting down trains and highways. Elsewhere, South Asia’s monsoon continues to produce the seasonal flood threat the region faces every summer, with rain-swollen rivers and landslide risk persisting across parts of India, Pakistan and neighboring countries. In the United States, a corridor of slow-moving thunderstorms tied to multiple shortwaves moving through the ridge-trough boundary is raising flash-flood concern across the Midwest and East into the weekend, with flood watches and warnings already posted in parts of the Ohio Valley and Appalachians.

Severe storms

A significant severe-weather outbreak swept through Ohio and the surrounding Ohio Valley on August 11, with multiple lines of storms producing widespread damaging winds and embedded tornadoes, including a confirmed EF1 tornado that tracked through the Columbus area. Forecasters expect the unsettled eastern U.S. pattern to continue generating rounds of severe thunderstorms into the weekend as successive shortwaves ride along the boundary between the southern ridge and the eastern trough, with damaging wind and hail the primary hazards. Farther west, monsoonal moisture wrapping around the same ridge is fueling scattered but locally intense thunderstorms across the Southwest and High Plains, capable of producing flash flooding and outflow winds even as the broader region bakes under record heat.

Jet stream patterns

The jet stream is currently split into a classic ridge-trough-ridge configuration that explains much of this week’s extremes. A strong upper-level ridge — the same feature driving the Southwest and Plains heat wave — is centered over the southern United States and is forecast to focus further over the Southwest and southern Plains as the week progresses. To its east, a parade of shortwave troughs is digging across the central and eastern U.S., fueling the thunderstorm and flash-flood threat from the Mississippi Valley to the Atlantic coast. To its west, an unusually active trough has developed in the eastern Pacific, a pattern feature more typical of autumn than mid-August. Across the Atlantic, a comparable blocking ridge is anchored over Central Europe, while the polar jet has buckled southward over the Southern Hemisphere’s mid-latitudes, opening the door for the cold outbreaks now gripping South Africa and southeastern Australia.

Atmospheric rivers

Atmospheric river activity is typically dormant in mid-August, but the unusually active trough now digging into the eastern Pacific is forecast to send a plume of Pacific moisture into the Pacific Northwest and Northern California from late Wednesday through the weekend, with the heaviest impacts expected Thursday. Coastal Washington, Oregon and the Cascades could see 2 to 4 inches of rain, with isolated totals up to 6 inches near the coast, while interior areas of the Northwest, Idaho, Montana and Wyoming should see 1 to 2 inches; heavy, wet snow is possible above pass level in the Cascades and Sierra. Wind gusts up to 50 mph are possible along the coast, and forecasters are warning that the rain could fall quickly enough to trigger localized flooding and mudslides despite being a welcome dent in ongoing drought across the interior Northwest. It’s a modest, early-season event by winter AR-parade standards, but notable for arriving well outside the region’s typical October-through-April atmospheric river season.

Areas to watch

The Atlantic’s Invest 92L bears close watching as it tracks westward toward the northeastern Caribbean over the coming days, with a 70 percent chance of becoming a tropical depression or storm by this weekend — the season’s most credible threat yet, even as a strengthening El Niño is expected to suppress overall Atlantic activity into the fall. In the Western Pacific, the region is still absorbing the aftermath of Typhoon Dolphin, which raked Japan’s Ogasawara and Amami Islands, Okinawa, Taiwan and southeastern China in early August, and forecasters will be monitoring the basin for the next system to organize. Europe’s heat is expected to ease modestly next week as the ridge shifts east, though renewed building is possible; the U.S. Southwest should see some relief from the most extreme heat by the weekend before warmth returns to the Northeast and Pacific Northwest. Continued monsoon rains keep South Asia’s flood risk elevated, the unsettled eastern U.S. pattern bears watching for additional severe weather and flash flooding through the weekend, and forecasters will be tracking whether the Pacific Northwest’s early atmospheric-river pulse is a one-off or a preview of an active fall pattern to come.

Orbis Weather — Weekly Global Weather Watch is compiled from NOAA, National Weather Service, and other meteorological agency reporting alongside global news coverage of ongoing weather events.