It freezes, its slippery, car windows are frosted, but in De Bilt, no frost days have been recorded this winter. A frost day is when the temperature stays below zero for 24 hours. Due to the burning of fossil fuels, more CO2 is released into the atmosphere, warming the Earth and reducing the number of frost days in the Netherlands.
Frost Days in De Bilt
The number of frost days varies significantly from year to year, as shown in Figure 1. The height of the bars represents the number of frost days per year in De Bilt since 1906. The highest number was in 1942 with 46 frost days, followed by 1963 with 43.
Since the 1960s, there has been a declining trend. On average, the number of frost days decreases by about 1.5 days every 10 years. Sixty years ago, there were still around 11 frost days per year on average, but nowadays there are only about three. In 2023 and 2024, De Bilt even recorded zero frost days. The last frost day was December 17, 2022.
Frost Days are Becoming Less Cold
Not only do we count fewer frost days, but these days are also less cold. The color of the bars indicates the maximum temperature on counted frost days. The greener the bar, the less cold it is. The last time it stayed severely frosty (below -10 degrees) all day was January 14, 1987. The coldest frost day after 2000 was December 2, 2010, with a maximum temperature of -6.1 degrees.