The Danube valley between Passau and Linz breaks through the Bohemian Massif, which as a foothills of the Bavarian Forest and the Sauwald Forest creates a harsh low mountain climate.
Brook valleys form a connection from the Danube valley to the low mountain ranges and act as cold air corridors. Where these so-called Dobeln flow into the Danube valley, cold air areas with corresponding flora and fauna are created.
This is opposed by the mild climate of the Danube Valley itself:
The high heat storage capacity of the water causes mild winters.
The south-facing slopes make optimum use of solar radiation and convert it into heat.
The valley is normally between 200 and 300 metres deep, at the deepest point near Jochenstein even 600 metres (Haugstein, 895mNN) and provides a certain degree of wind protection.
This creates a high level of humidity, which in turn stores the heat well.
In comparison, the weather data from Rollhäusl/Untergriesbach (560 mNN) (www.meteo24.de) and Engelhartszell (295 mNN) (www.wetter.at) show this for example: on 5.12.2008, the wind speed in Rollhäusl was five knots with gusts of 10 knots at a temperature of 0.1°C, in Engelhartszell no wind was measurable at a temperature of 4°C. The wind speed in Rollhäusl was 5 knots with gusts of 10 knots at a temperature of 0.1°C, in Engelhartszell no wind was measurable at a temperature of 4°C.
The following climate districts apply in the region:
Southern German-Austrian district (mild transition stage, 380 – 600 m): mean annual temperature 6-7°C, annual precipitation 800 to 900 mm, number of frost days 90-100, duration of snow cover/days 100
Southern German-Austrian district (rough stage, 600-900 m): average annual temperature 5-6°C, annual precipitation 900-1000 mm, number of frost days 100-120, duration of snow cover/days 130