What was the weather like this year? Climate researcher Peter Siegmund (62) from the KNMI does not have to think long. 2023 may be the warmest year ever measured in De Bilt, together with 2014 and 2020, he says. And it is probably the wettest year nationally since the meteorological institute started measuring precipitation in 1906. The winter was mild, says Siegmund, without severe frost and snow and with the warmest New Year’s Day ever recorded: 15.6 degrees Celsius. Spring and autumn were exceptionally wet, the second half of May and the month of June exceptionally dry.
This year’s weather summarized in one word? “Variety,” says the researcher.
Upon request, Siegmund comments on the most extreme weather days of the year, as measured in De Bilt. Even if he is careful, the year is not over yet.
Wettest day: January 12
Because the Netherlands is warming up, it rains more in winter. On January 12, an extremely warm winter day with a daily average of 10.3 degrees Celsius, it rained for a total of 18.6 hours and what Siegmund calls “an incredible downpour of water” fell: 40 millimeters.
The excessive rainfall caused flooding. When the Rivierenland Water Board decided to protect Gorinchem and drain the water via the Linge, that river overflowed its banks. Seven LRC football players made it to the national press because they placed sandbags in front of the home of an elderly couple in Leerdam who were threatened by the rising water.
With a total of about 1,100 millimeters, about 30 percent more rain fell this year than usual.
Whitest day: January 20
Traffic jams and accidents due to winter showers, faulty switch heating at the NS – these occurred sporadically this year. The only day with a snow cover in De Bilt (normally 10 days) was on January 20. Three centimeters fell, just enough for tiny snowmen.
Coldest day: January 21
With a daily average of minus 1.4 degrees Celsius, January 21 was the coldest day of this calendar year. How mild the winter was is evident from the small number of days that motorists had to work with ice scrapers. The KNMI measured only 41 frost days (minimum temperature below 0 degrees, normal 53) and exactly zero ice days (maximum temperature below 0 degrees, normal 6 days). The lowest measured minimum temperature was also of little significance: minus 5.6 degrees Celsius on March 1.
Siegmund dares to make the prediction: he will no longer experience the Elfstedentocht. Due to global warming, the chance of severe frost, such as on February 4, 2012 when it froze to 23 degrees, is increasingly smaller, he says. “The Arctic is warming even faster than the Netherlands. We have southwesterly winds more often. And what doesn’t help is that the water in ditches, canals and ponds is getting warmer. This combination ensures that it takes longer before a suitable ice floor is created.”
Sunniest day: June 10, 11, 13, 14, 16, 25 and July 7
Around the longest day of the year, June 21, the KNMI measured seven days with 15.3 hours of sunshine. A good month for solar panel owners: on average across the Netherlands, June was the month with the most solar radiation ever measured. Residents of Gelderland, Overijssel and Flevoland had to switch off their solar panels in mid-June because they could not supply the generated electricity back to the electricity grid.
Due to global warming, temperatures have risen in all months, says Siegmund. “The month of June is now as warm as July in the climate of 1930. This makes June the new July. And so you can also say that September is the new June.”
Driest day: June 12
The KNMI also measures humidity. The institute uses this indicator for the amount of moisture in the air, among other things, for weather models. With a daily average of only 37 percent, June 12 was the driest day of the year.
The persistent sun and lack of rain – in mid-June not a drop of rain had fallen in De Bilt for 33 days – caused a record drought and all kinds of problems. Farmers were no longer allowed to irrigate their fields, the prices of cauliflower and other vegetables shot through the roof and fire brigades called on nature lovers and recreationists to be alert to wildfires.
Hottest day: July 8
With a daily average of 24.7 degrees Celsius, July 8 was the warmest day. This year there were 38 summer days (maximum temperature 25 degrees or more), ten more than normal. For what was probably the warmest year ever, together with 2014 and 2020, there were remarkably few tropical days (+30 degrees): five, the average. The highest temperature measured, 32.2 degrees Celsius, was also not remarkably high. Siegmund: “This extremely warm year is a bit sneaky came about: it is mainly due to the high temperature on normal days.”
Windiest day: November 2
Storm Ciarán (named after Ciarán Fearon, an Irish civil servant who keeps track of water levels) disrupted daily life on November 2 with hourly averages of up to 22 meters per second (wind force 9). Locks were closed as a precaution, ferries were taken out of service and trains did not run. The Dutch Championship against wind cycling over the Oosterscheldekering was cancelled. The reason: too strong wind.
Storm Poly on July 5 was one of the strongest summer storms in more than fifty years. The only time this year, says Siegmund, that the KNMI warned with the weather alarm ‘code red’.