The intense heat that has dominated much of the US over the past week shows little sign of easing over the coming days as high pressure continues to be anchored across the western half of the country, and this is likely to spread towards the east coast by Thursday.
In Phoenix, Arizona, temperatures are expected to remain rooted in the high 30Cs this week after the city experienced a record-breaking 40.5C (105F) on 20 and 21 March. Such readings are highly anomalous for March: the last occurrence of 100F, or just under 38C, here in this month dates back to 1988. The National Weather Service said the threshold was typically not reached until late May, highlighting the unusual intensity of this event.
Record-breaking temperatures have been recorded widely across the western US as the daytime maxima exceed 15C above the climatological norm. In Denver, Colorado, the typical March daytime maxima is in the mid-teens Celsius, yet on Saturday temperatures reached 30C. This was the first time 30C had been reached and the city’s highest March temperature since 1971, when 28.9C was recorded, with still the rest of this working week to see the daytime highs reach close to 30C again.
In stark contrast, conditions across Canada are set to turn sharply colder as a surge of Arctic air spills southwards. This cold plunge is enhanced by the high pressure over the western US, creating a dramatically meandering jet stream pulling these polar conditions south into Canada. Temperatures are expected to fall more than 10C below seasonal norms, with daytime highs struggling to rise above freezing in many major cities this week. Thursday 26 and Friday 27 are expected to be the coldest days this week, when Saskatoon, Saskatchewan, Quebec City, Quebec, and Edmonton, Alberta, could see maximum temperatures of just -9C, -7C, and -6C respectively.
Meanwhile, authorities in Tenerife activated emergency plans as Storm Therese, named by the Portuguese weather service, swept across the Canary Islands late last week. Tenerife was among the hardest hit: a state of emergency was declared and Spain’s meteorological agency, Aemet, issued orange weather warnings covering much of the island through Friday and into Saturday. Northern areas experienced wind gusts of about 60mph, while the south had heavy rainfall. The Lomo del Balo weather station on the south-west of the island recorded 35.2mm on 19 March, while some personal weather stations recorded up to 100mm on the southern slopes of Mount Teide, near Vilaflor. The storm also brought some snow to higher elevations.
In response, flights to and from Tenerife were cancelled or diverted as conditions worsened and schools were closed on Thursday and Friday. More than 1,000 emergency personnel were deployed to protect residents and manage the impact. Conditions have since calmed down, but the weather will remain unsettled over the next few days with heavy showers and thunderstorms, potentially bringing another 90mm of rain cumulatively from Sunday to Thursday.
