Unusual US Heatwave Persists as Canada Braces for Arctic Blast
An intense heatwave that has dominated much of the United States over the past week shows little sign of easing in the coming days. High pressure remains anchored across the western half of the country and is expected to spread towards the east coast by Thursday, maintaining elevated temperatures.
Record-Breaking Heat in the Western US
In Phoenix, Arizona, temperatures soared to a record-breaking 40.5 degrees Celsius (105 degrees Fahrenheit) on March 20 and 21. Such readings are highly anomalous for March, with the last occurrence of 100F in this month dating back to 1988. The National Weather Service noted that this threshold is typically not reached until late May, underscoring the unusual intensity of this event.
Phoenix is forecast to remain in the high 30s Celsius this week, while other parts of the western US have also experienced extreme heat. Record-breaking temperatures have been widespread, with daytime maxima exceeding 15 degrees Celsius above climatological norms.
In Denver, Colorado, temperatures reached 30 degrees Celsius on Saturday, marking the first time this level has been achieved in March and the highest March temperature since 1971. The typical March daytime maximum in Denver is in the mid-teens Celsius, yet the rest of this working week is expected to see highs close to 30 degrees Celsius again.
Arctic Cold Surge in Canada
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, which creates a dramatically meandering jet stream pulling polar conditions into Canada.
Temperatures are expected to fall more than 10 degrees Celsius below seasonal norms, with daytime highs struggling to rise above freezing in many major cities this week. Thursday, March 26, and Friday, March 27, are anticipated to be the coldest days, with Saskatoon, Saskatchewan, Quebec City, Quebec, and Edmonton, Alberta, potentially seeing maximum temperatures of just -9 degrees Celsius, -7 degrees Celsius, and -6 degrees Celsius, respectively.
Storm Therese Impacts the Canary Islands
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, with a state of emergency declared and Spain's meteorological agency, Aemet, issuing orange weather warnings covering much of the island through Friday and into Saturday.
Northern areas experienced wind gusts of about 60 miles per hour, while the south had heavy rainfall. The Lomo del Balo weather station on the south-west of the island recorded 35.2 millimetres on March 19, with some personal weather stations recording up to 100 millimetres 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 90 millimetres of rain cumulatively from Sunday to Thursday.
This analysis highlights the extreme weather patterns affecting North America and the Atlantic, with persistent heat in the US, a severe cold snap in Canada, and stormy conditions in the Canary Islands, all driven by complex atmospheric dynamics.
