The Koeppen-Geiger classification suggests the climate of The Netherlands can be classified as a warm temperate humid climate with the warmest month lower than 22°C over average and four or more months above 10°C over average. The year, however, our summer arrived in the middle of the winter and it just keeps getting warmer. We are on course to be subtropical in the next 10 years, a similar climate to North Africa, Southern Spain or Northern Florida.
Today, on the West coast of Holland where I live, we have entered the 9th day in a row when temperatures have hit the mid-to-high 30sC (100+F). Because Holland is so humid the actual temperature feels like 50 deg C, 122F and has been mostly unbearable. Last night, for instance, the temperature at bedtime was still above 30 deg C (86+F) rendering sleep impossible. The last 9 days is the second heatwave we have endured this summer.
The measured solar radiation (sunshine) between mid-March and mid-June was about 3 per cent higher than the average over the same period in the past four years. Since the measures against the spread of the coronavirus were announced, more solar radiation, (sunshine) has been able to reach the Earth's surface. This is evident from research by KNMI and TU Delft, however, a whole month before March arrived something strange happened to the Dutch weather.
This year our summer arrived in the middle of the winter. In the first week of February temperatures here in Holland reached a balmy 20 deg C (68F). My wife and I enjoyed the weather as we sat outside in the winter sun, it was glorious and something I had never witnessed before and since the beginning of February, the sunshine and indeed the summer has continued to provide day after day, hour after hour of sunshine.
A hundred years ago, the number of tropical days averaged just over one per year according to the KNMI. In recent years, there are around five per year. However, we have just entered the 9th tropical day in a row and the outlook is for the tropical weather to last well into next week. The highest maximum temperature of the year has increased much faster than the global average temperature since 1901. This aspect of summer is not exceptional in the expectation for 2020: the temperature of 33 to 34 degrees expected for Saturday, August 8, occurs more often than not today. Three-day average heat, which is more relevant to health, is no longer exceptional this year due to the sharp increase over the past century and it's getting more extreme every year.The number of tropical nights is also increasing of course. Minimum temperatures of 18 degrees or more are about three times as common this century as in the second half of the last century according to KNMI. In Vlissingen, for example, in 1951-2000 the minimum night temperature was 18 degrees or more on average four times a year, while this century was an average of thirteen times a year and rising. The relative increase in the number of tropical nights, with minimum temperatures of 20 degrees or more, is even greater making sleep difficult.