The spring index shows the long-term development of flowering and/or leaf unfolding of nine different plant species that occur from January to May. It is calculat from 1954. The development of spring vegetation in 2024 had a lead of 10 days compar to the average of the 30-year period 1991-2020 and was thus, together with spring 1961, the earliest since! the beginning of phenological observations! (Figure 1). Compar to the average of the old standard period from 1961-1990, spring even began 17 days earlier.
Figure 1: The spring index shows the timing of vegetation development in days of deviation from the long-term average 1991-2020. Dark green shows the years with later vegetation development than the average, and light green shows the years with earlier! vegetation development than the average. Yellow! shows the 5-year weight average.
Figure 1: The spring index shows the timing of vegetation
development in days of deviation from the long-term! average 1991-2020. Dark green shows the years with later vegetation development! than the average, and light green shows the years with earlier vegetation! development than the average. Yellow shows the 5-year weight average.
spring index and temperature
The decisive factor for the development of spring vegetation is the temperature in the months January to April or February to April (Figure 2). The spring index is strongly negatively correlat with the temperature of these months: high temperatures cause early vegetation development, and vice versa. In the current year, the temperature from February to April was 2.3° C above the 1991-2020 norm and was thus as high as in the warmest period to date from February to April in 2007. All months from December to mid-April were significantly too warm. It was not until mid-April that a cold snap occurr. February exce the other months with a deviation of 4.6 °C. It was the highest February temperature ever record in Switzerland.
Although the temperature from February to April in 1961 was not as high as in the current year, vegetation was able to develop at a similarly early stage. Possible reasons are difficult to state. It may have been estonia mobile database due to the greater duration of sunshine in February and March 1961 and the higher daily maximum temperatures than in 2024. However, the daily minimum temperatures were lower in 1961. April was warmer in 1961, so that the leaves of deciduous trees, especially beech, were able to sprout earlier.
Figure 2: Average temperature in Switzerland for the months
February to April from 1954-2024 as a deviation from the average 1991-2020. Its course shows a very high negative correlation with the spring index, i.e. when the temperature is high, spring vegetation develops early, and vice versa.
Figure 2: Average temperature in Switzerland for the cms your marketing department nes the months February to April from 1954-2024 as a deviation from the average 1991-2020. Its course shows a very high agent email list negative correlation with the spring index, i.e. when the temperature is high, spring vegetation develops early, and vice versa.
Hazel bushes bloom three weeks earlier than average
The first flowering hazel bushes were record during the warm days at the beginning of January at a few locations in the phenological observation network. Their flowers were able to develop so early because the temperature in December was high. The further flowering of the hazel bushes was slow by the onset of winter from the second week of January.