The most significant meteorological event unfolding this Wednesday is a cyclogenesis forming over the central-eastern plains of Argentina, a deep low-pressure system that is already lashing the Buenos Aires metropolitan area with torrential rain, frequent lightning, and gusts that could exceed 70 kilometres per hour. The Servicio Meteorológico Nacional has issued orange and yellow alerts for the capital and a swathe of provinces from La Pampa to Santa Fe, warning of localised flooding and possible hail. Viewed from Buenos Aires, the concern is less about the immediate afternoon downpours and more about the persistence of the system: forecasters expect the instability to linger through the weekend, bringing a sharp drop in temperatures after Thursday, with maxima falling to around 14 degrees Celsius by Friday.

Across the Andes, a completely different set of hazards prevails. The viento Zonda — a dry, dusty foehn wind — is sweeping down the eastern slopes of the cordillera into Mendoza, San Juan, La Rioja and Catamarca, with orange-level warnings for gusts up to 90 km/h and a sudden, oppressive rise in temperature. In Mendoza, authorities have suspended afternoon classes in the capital and several departments, shifting learning online. Yet further south in Neuquén, the same frontal system that triggers the Zonda in the north is depositing up to 70 centimetres of snow in high-altitude areas, with a risk of whiteout conditions.

North of the equator, Mexico is in the grip of a second heatwave that is already breaking records. The Comisión Nacional del Agua reports temperatures above 45 degrees Celsius in Guerrero and parts of San Luis Potosí, while the capital, Mexico City, is bracing for a peak of 34 degrees — an exceptionally high figure for early May. The heat has prompted the extension of the Hoy No Circula vehicle restriction programme in the metropolitan zone, as officials struggle to contain ground-level ozone and particulate pollution. In Jalisco, Guadalajara is forecast to reach 36.7 degrees; in Yucatán, Mérida could touch 41 degrees. The anticyclonic circulation aloft that drives this heat shows no sign of weakening until at least Friday, according to analysts in Mexico City.

Elsewhere in the northern hemisphere, conditions are calmer but still noteworthy. In Spain, the Agencia Estatal de Meteorología predicts a largely stable day across the peninsula, though the northern fringe — from the Pyrenees to the Aragonese mountain range — will see showers and isolated thunderstorms, with snow on high peaks. Morocco’s Direction Générale de la Météorologie warns of locally stormy cloudbursts over the Atlas and the Oriental region, accompanied by strong gusts and dust. In Russia, Moscow is enjoying a spell six degrees above the climatic norm, with temperatures forecast to hover around 20 to 22 degrees through Friday — warm enough to feel anomalous, even if it does not quite meet the definition of a formal heatwave.

Looking forward, the Argentine cyclogenesis will remain the focal point for the southern cone through the end of the week, slowly dragging cold air northward and finally breaking the unseasonably mild autumn that preceded it. For Mexico, the immediate outlook is one of sustained heat, but models suggest a gradual moderation from the weekend, as a trough from the Pacific edges into the Gulf. What is striking about 6 May is how the same planetary-scale circulation — a wavy jet stream amplified by a stubborn blocking pattern — simultaneously generates extreme heat, torrential rain, fierce winds and alpine snow across the hemisphere. The pattern is not unprecedented, but its intensity and geographic breadth are a reminder that the climate system, even in its day-to-day variability, is now operating on a warmer and more energetic baseline.