Temperature averages for 14-16 Sept in Varese

Paolo Valisa - CGP

We have selected some relevant data from the meteo-climatic database of CGP that starts from 1967. As the temperature has been steadily increasing since then, we evaluated the average values only for the last 20 years (2011-1992) for the period 10-20 Sept in Varese.

The average temperature is 18.0°C/64.5°F .
The average maximum temperature is 22.1°C/72°F .
The average minimum temperature is 13.3°C/56°F .
The highest temperature for the period was 30°C/86°F (1987/09/18).
High temperatures are not uncommon in later years. In 2011 the absolute max temperature of the period was 29°C/84 °F (2011/09/14).
The lowest maximum temperature was 11.5°C/53°F (1996/09/19).
The lowest minumum temperature was 6°C/43°F (1994/09/19).

Rain and cloud coverage

During the period 10-20 September (last 20 years) the probability of a rain day is 30% (rain > 1 mm) and the average total rain is 79 mm .
The maximum rain recorded in only one day was 258.6 mm (1995/09/13 ), followed by 113 mm (1992/09/10) and 110 mm (2009/09/16). The return time for the 258.6 rain is about 75-100 years. In our web pages can be found, for interested readers, a detailed study on return time for Varese rain series .
Despite some rain events, in the period 10-20 September, sunny days were 44% , cloudy were 30% and partly cloudy 26% .

Average wind direction and speed

The average wind speed over Varese lake is often quite low and, as is shown by the hystogram, there is more than 60% time of calm or wind speed less than 1 m/sec. This is expecially true during the night. In daytime during fair weather some breezes rise, depending on lake boundary insolation and orientation. Strong winds reaches the lake only few days per month, usually due to downslope Northern wind that cames from the Alps. In such conditions waves can soon develop on the surface. Thunderstorms in summer (may-september) also can originate strong irregular gusts. The maximum wind speed during a thunderstorm recorded so far at Schiranna meteorological station was 29.2 m/sec (105 Km/h) on 2012 aug 22.

Breezes speed (blue) and direction (red) in Bodio during a week of fair weather (10-17 aug 2012)

Example of breeze recording during a week of fair weather (10-17 aug 2012) for the stations of Bodio (left) and Schiranna (right), respectively at the North edge and South edge of the lake. Wind speed is blue, wind direction is red.

A further analysis of wind breezes is relevant because these are frequent and constant winds over the lake. Breezes depend on the surrounding mountains (expecially in the North side) and are particularly sensitive to the orientation of the lake boundaries. Breeze direction, for example, is not the same for Bodio and Schiranna meteorological station. Bodio lies in the southern part of the lake. Daytime breezes are mainly from N to NW starting around 10 am to 18 pm and reaching an average speed of 2 m/sec.
In Schiranna, thermal driven breezes are more regular due to the presence of the Campo dei Fiori mountain in the North. Direction is mainly SW-W during the morning, W at noon and W-NW in the afternoon. Average speed is 1.5 to 2 m/sec.