It has been the seventh warmest April since the series began in 1965 and the sixth warmest in the 21st century. And it has been largely warm due to the role played by the minimum daily temperatures, which were 2.3ºC above the normal value. Thus, last April was the third month of April with the highest average minimum temperature since 1965, behind only the months of April 2011 and 2014.
It is worth noting, furthermore, that the year from May 2019 to April 2020 has been the longest period of consecutive months with positive anomalies in their average monthly temperatures since the beginning of the series, in 1965.
The most outstanding thermal anomalies of the past month, all of a positive nature, marked values close to + 3ºC in the extreme north of the peninsula, specifically in areas of Cantabria, the Basque Country, northeastern Castilla y León, northern Navarra and points in the Aragonese Pyrenees and Catalan.
A review of the ephemeris takes us down to the minimum temperatures. Thus, in 11 main stations the average of the daily minimum temperatures was the highest for a month of April since the beginning of the respective series. Likewise, at the main station of Palma de Mallorca / airport, a minimum temperature of 16.8ºC was observed on the 19th, which was the highest on an April day since the beginning of the series.
The small daily thermal oscillation observed in April stands out, 1.8ºC lower than the normal of the month: the minimum daily temperatures were on average 2.3ºC above the normal value and the maximum daily temperatures were only 0.5ºC above normal value for April.
These minimum temperatures, well above their normal value, are what dragged and motivated April to be declared as very warm. This point is key to understanding a concept that may seem antagonistic at first, such as the fact that last April was very warm but at the same time very scarce in hours of sunlight.
Spain, the European country with the fewest hours of sunshine during quarantine
The average hour of sunshine in April 2020 in Spain has been 171.4, which is 58.2 hours below the monthly average and makes it the second least sunny April since 1983.
It is necessary to mention what happened between March 15 and April 23 due to its special climatic uniqueness and also coinciding with much of our period of confinement. During this time interval Spain received very few hours of sunshine, being the country in Europe and North Africa that registered the least insolation during these 40 days. At the other extreme we have Hungary, Slovakia, Luxembourg and Germany, which recorded an average of more than 370 hours of sunshine, compared to 223 in Spain.
Within Spain, in several observatories located on the shores of the Mediterranean such as Valencia, Castellón or Malaga, this has been the period of 40 days with the fewest hours of sunshine in its entire historical series, and in many others it is among the three least sunny. The cause of the insolation shortage was a situation of Scandinavian anticyclonic blockade, which was persistent at the beginning and end of the period and which, in general terms, encouraged the circulation of storms on the Peninsula with all its associated cloud structures.
A very humid month
Overall, April was very humid, with an average rainfall over Spain of 91 mm, a value that exceeds the normal value of the month by 40%, which is 65 mm (reference period 1981-2010). With the information available, April 2020 is ranked 11 in the corresponding series since 1965, starting with the wettest and seventh as far as we have been in the 21st century.
As for the percentage of precipitation with respect to the normal value, most of the territory has been above said values. Rainfall has exceeded three times normal values on the Mediterranean coast of the Gerona and Barcelona provinces, southwest of Cáceres and in some parts of the Balearic Islands. On the contrary, in the northwest of Asturias and in some areas of Cantabria and the Canary Islands, rainfall did not reach half of normal values.
The highest daily rainfall in April between main observatories was recorded on the 19th with 79 mm at Barcelona / airport, followed by the 24th with 71 mm at Rota / Naval Base, on the 21st with 64 mm at Girona / airport, on the 15th with 52 mm in the Port of Navacerrada, on the 16th with 50 mm in Vigo / airport and on the 18th with 48 mm in Soria. The maximum daily rainfall mentioned in the Rota / Naval Base and Soria observatories, together with the 35mm precipitation recorded in Madrid / Torrejón on the 18th, have supposed the highest values of the corresponding series in April.
Regarding the total precipitation of the month, also in two observatories the previous highest value of the corresponding series has been exceeded: Barcelona / airport with 264 mm and Valladolid with 114 mm. In addition, in several main observatories the highest number of rainy days and storms of the corresponding series was recorded in a month of April.