It’s not the first time recently that chilly conditions have gripped parts of southern South America in the lead-up to the southern hemisphere winter. Over the past couple of days, an area of low pressure has positioned itself just south-east of the continent and allowed cold air to filter northwards into southern Chile and Argentina. This process will continue over the coming days with temperatures 5-10 degrees below normal in Argentina from Thursday.
In fact, the western side of South America, including farther north into Peru, has experienced almost perpetually cool conditions of late linked to an ongoing La Niña event in the Pacific Ocean. During these events, which usually occur every few years, sea surface temperatures (SSTs) in the south-eastern Pacific cool significantly as colder waters from the deep upwell to the surface. Current observations suggest SSTs just off the coast of Peru are between 1.5 and 3.5C colder than normal and they have been cooler than normal since last autumn. The presence of cooler water has an often moderating impact on temperatures in South America but can have wider-ranging impacts on global weather patterns too.
One such link suggested by research is that with drier-than-normal weather over the southern US during the winter half of the year. Since January, conditions have been drier than normal across the desert south-west. For the likes of Arizona, critical fire risks are in place for Tuesday and the return of windier and warmer weather for the weekend suggests these may continue to be a feature in the short term.
Meanwhile, an exceptionally warm airmass that affected Iberia – bringing maximum temperatures over 40C in parts of southern Spain on Friday and Saturday – is moving eastwards across southern Europe. Further heat is expected to continue from Tuesday and over the next few days across Italy, Greece and the Balkans. While temperatures won’t be quite as high as in Spain, the aforementioned areas will still be prone to at least the low to mid-30s Celsius for a couple of days, in parts 10 degrees above the seasonal norm.