As a general rule, weather-related closures of the Danube waterway may either result from strong icing or serious high water conditions. Strong icing may result from sustained temperatures well below freezing point. Ice impedes navigation mainly during the months of January and February. High water conditions are the result of fast snow melting or heavy rainfall and mostly occur at the beginning of spring or in midsummer. During these official weather-related closures, navigation on the Danube is prohibited.

In 2010, the Austrian section of the Danube waterway was open to navigation on 361 days or for 98.9% of the year. In this year, due to high water levels at the beginning of June, parts of the Austrian Danube had to be closed to navigation for a period of up to four days. However, 2010 did not witness any significant ice formation on the Danube.

Using the long-term annual average from 1995 to 2010, the Austrian section of the Danube waterway was open to navigation on 98.2% of the days or on 359 days per year.

Low water events do not require the waterway to be closed to navigation. However, in this case the usability of the waterway for cargo transport is restricted in terms of efficiency. The relationship between the potential capacity utilisation of cargo vessels and the available fairway depths is described in greater detail in the following chapter «Fairway Conditions».

Transport to and from the west not only depends on the Austrian and German sections of the Danube waterway, but also heavily relies on the availability of the Main-Danube Canal, linking the Danube with the Main and Rhine. A closer examination reveals that the availability of this waterway link is not quite as good as that of the Danube waterway. Although there are normally no closures due to high water on the Main-Danube Canal, ice-related closures occur more often than on the Danube. In addition, maintenance and modification works are undertaken in some years which last for about two weeks and necessitate the closure of the canal.

In the first quarter of 2010, the Main-Danube Canal was closed to navigation for 35 days due to icing (from 26 January to 1 March). An analysis of the closures that occurred during the last 15 years shows an average annual availability of the Main-Danube Canal of 344 days or 94.2% of the year.