Thursday 20 April: Late frost but not in the city
Spring started very mild with a record high average temperature in Ukkel for March. But during the previous days a northern flow transported cold air (about -5°C at 850 hPa = about 1.5 km height) towards the Benelux. Combined with the calm and nearly clear conditions all ingredients were presented for strong cooling last night. As feared (by the agricultural sector) this resulted in widespread negative temperatures this morning in Belgium.
A map of the 2m temperatures in Gent at 7h00 local time, shortly after sunrise and thus more or less the time to measure the minima, is shown. In Melle we measure a temperature of -2.7°C and also at the suburban location of Wondelgem there are slightly negative temperatures. The urban heat island phenomenon causes the temperatures to remain clearly above the freezing point in the more urbanized parts of Gent. At the Provinciehuis for example the temperature is still 3.5°C or thus more than 6°C warmer than Melle. A large differences for the plants in the city...