July rainfall almost 3x more than normal

On 14 July, it rained more in 12 hours than the average for the entire month of July over the past 30 years Photo: Matic Zorman / Maison Moderne

On 14 July, it rained more in 12 hours than the average for the entire month of July over the past 30 years Photo: Matic Zorman / Maison Moderne

One hundred and eighty-eight litres of water per square metre: this is what fell on Luxembourg during the month of July, according to Meteolux figures. In contrast, the July average over the last three decades was only 71.5 l/m².

Expressed as a percentage, this July had 260% more rain than the average July since 1991. It didn’t set the record, however: “In fact, it was the second wettest since records began in 1947," explains Luca Mathias, meteorologist at Meteolux. The record is held by the year 2000 with 197.2 l/m².

42% of the month’s precipitation in 24 hours

The difference, as can be seen in the graph in the above tweet, is that July was mainly plagued by the torrential rain that fell in the space of a few hours on 14 July, which caused extensive flooding and damage. Forty-two percent of the total rainfall for the month (79.4 L/m²) fell in under 24 hours. This beats the records for 12-hour (74.2 L/m²) and 24-hour (79.4 L/m²) rainfall. It therefore rained more in 12 hours on that day than the average for an entire month of July over the last 30 years!

All of these figures were taken at the Findel airport. “They are therefore not representative of what happened in the whole country. But they do give an idea,” says Mathias.

However, some places in the country were even more heavily soaked than Findel. “This is shown by the statistics of the Administration of Technical Agricultural Services, which has dozens of stations throughout Luxembourg.”

Other figures published in the Meteolux monthly summary also show that it was cooler than usual.

“With a monthly average temperature of 17.2°C, July 2021 was 1.5°C below the normal temperature for the period 1991–2020 (18.7°C),” the meteorologist comments. “However, it is not unusual to have a July with a monthly average temperature of around 17°C. In the history of our station, the coldest July ever recorded was in 1954, with 13.8°C.”

Only three “summer” days

Notably, this year only three “summer” days (i.e. with maximum temperatures of 25°C or more) were recorded in July. “Whereas the long-term average for 1991–2021 is 12.8 days. And no hot or very hot days were observed.”

All this leads to a 21% deficit in sunshine compared to the 1991–2020 average: 203.6 hours versus a norm of 257.6 hours. “This is still a far cry from July 1980, the month with the lowest sunshine levels ever recorded at our station, with only 125.3 hours on the clock,” concludes Mathias.

This article was originally published in Paperjam. It has been translated and edited for Delano.