VARESE – After a May with accumulations of rain two or three times higher than the normal climate of the month for the thirty-year period 1991-2020, from tomorrow, Wednesday 5 June, in Lombardy we will have mainly sunshine with an increase in temperatures. This drier and warmer phase, characterized in the plains by sunshine and temperatures close to 30°C, will not prevent the possibility of afternoon showers in the Alps and Pre-Alps. From Sunday 9th, however, there will be a probable return of rain.
Rainy May
The month of May, due to a vast area of low pressure between the British Isles and France which brought humid and unstable winds to northern Italy, was a very rainy and relatively cool month in all the Lombardy provinces.
In detail, the data recorded by the Arpa Lombardia monitoring network on the main Lombard cities, relating to the rainfall in May 2024.
- Milan 321 mm (May), 96 mm (average 1991/2020) +234 percent (compared to the average).
- Pavia 223 mm (May), 67 mm (average 1991/2020) +233 percent.
- Persico Dosimo (Cr) 248 mm (May), 76 mm (average 1991/2020) +226 percent.
- Bergamo 341 mm (May), 110 mm (average 1991/2020) +210 percent.
- Mantua 187 mm (May), 69 mm (average 1991/2020) +171 percent.
- Varese 476 mm (May) 181 mm (average 1991/2020) +163 percent.
- Brescia 213 mm (May), 97 mm (average 1991/2020) +120 percent.
- Sondrio 174 mm (May), 92 mm (average 1991/2020) +89 percent.
Record numbers
The rainfall recorded is therefore higher than the average for May. The most important anomaly concerns the western plain, between Milan and Pavia, where more than three times the typical rainfall for the period fell, while it was more contained in the Alps, almost double, as shown by the Sondrio weather station. Almost everywhere, the day with the highest accumulation was May 15, when 97 mm fell in the city of Milan and peaks of over 150-170 mm were recorded in the province and in the Lodi area. If we extend the analysis from the 50s of the last century, it emerges that the month just passed is, for many places, in the ranking of the rainiest months of May: for example, in Pavia it appears to be the rainiest month of May, while the third in Mantua and Milan.
The Milan case
The record-breaking period began around mid-February. In Milan, since the beginning of 2024, 883 mm have been recorded, a value that is unprecedented in the last 261 years of history (measurements at the Brera Observatory began in 1764). If we consider that the average annual cumulative in Milan is around 910 mm, this data takes on even greater importance. In the first five months, the rain that normally falls in the course of a year has already fallen.
The temperatures
Again in the Lombardy capital, the rains mainly influenced the maximum daily temperature values, but the average temperature in May was slightly lower than the average temperature for the period 1991-2020 (as also in the rest of Lombardy albeit with slight differences).
From June 1st (the start date of the meteorological summer) the daily publication of “HUMIDEX” began again. The bulletin, prepared by the Agency’s Meteorological Service until 15 September, predicts heat discomfort due to the combined effect of temperature and humidity. The document reports, for each province, the level of discomfort detected the previous day and that expected for the current day and for the following two. The forecast refers in particular to the flat and urban areas of each territory most exposed to muggy conditions.
