On Monday 9 March, severe thunderstorms affected parts of southern France, with several departments including Hérault, Var, and the Alpes-Maritimes put under yellow alert for heavy rain.
Some of the heaviest rainfall totals came from a cell that passed over the Var department. Examples of high rainfall totals taken from some private weather stations come from the towns of Carqueiranne and Saint-Mandrier-sur-Mer, where 104.4mm was recorded in seven and a half hours, and 92.7mm in three hours respectively. However, as these are private weather stations, they may contain measurement errors.
The official Hyères weather station recorded 113.7mm within 24 hours, which makes these values seem credible. This marks a new record for the station, beating the previous daily March record of 84.1mm in 1988.
Furthermore, owing to this heavy rain, the Gapeau River in Var burst its banks. The river reached heights of 2.34m, approaching the 2.66m recorded in the November 2011 floods, and as a consequence flooding continued for the following few days.
The US has experienced an active few days of severe convective storms, including heavy rain, tornadoes, and large hail. The state of Illinois may be in line for a new hail size record. On Tuesday, a 6in hailstone was reported by a resident in the city of Kankakee, which if verified would mark a new state record. The previous state record was 4.75in, recorded in the village of Miniooka in June 2015. Other reports have been made of hailstones breaching this diameter, so a new record will probably be made official soon.
A persistent region of high pressure has resulted in record-breaking heat across the Namakwa district and Western Cape province of South Africa, with many weather stations shattering their all-time March temperature records.
The strong anticyclone resulted in the formation of a “heat dome”, where descending air beneath this area of high-pressure continuously compresses and warms over the course of days, resulting in very dry and hot conditions. Notable new March temperature records include a reading of 42.1C being recorded in Cape Town city, more than 2C warmer than the previous record of 39.8C, set in March 2015.
