Map from Google - Austria

In Austria, a country largely covered by mountains and hills, we can distinguish between three types of climate: the continental climate of the flat narrow region of Vienna, similar to that of East-Central Europe, with cold winters and warm summers, sometimes sultry; the climate of the other major cities (Salzburg, Graz, Linz, Innsbruck), located on lower mountains and hills, with cold winters and fairly warm summers, which are rainy and thunderous as well; and finally the mountain climate of the highest altitudes, cold and snowy in winter, cool and thunderous in summer. With respect to its Alpine "twin", Switzerland, Austria has a colder climate in winter, because of the greater distance from the Atlantic Ocean, and also the proximity to Eastern Europe.
Here are the average temperatures of Vienna.
Average temperatures - Vienna
Min (°C)-3-215101315151162-2
Max (°C)35101520232626211584
Min (°F)272834415055595952433628
Max (°F)374150596873797970594639

Precipitation is abundant in the mountains, where it exceeds 1,000 millimetres (40 inches) per year almost everywhere, and often 1.500 mm (60 in), while it's lower in the Vienna area, where only 535 mm (21 in) per year fall. However, rainfall is well distributed throughout the year, with a summer peak, because of the fairly frequent thunderstorms.
Here is the average precipitation in Vienna, which is located in the least rainy area of the country.
Average precipitation - Vienna
Prec. (mm)303035405560605050354535535


Winter in Austria is cold everywhere, even in the Danube valley, but especially in the valleys located at higher altitudes, and of course especially in the mountains. In Vienna, the Austrian capital, the average temperature in January is around 0 °C (32 °F), but in cities located at higher altitude and in valleys among the mountains, the averages are even lower: in Klagenfurt, the capital of Carinthia, 450 metres (1,500 feet) above sea level, the average temperature in January is -4.5 °C (24 °F).
Fog and low clouds are common in the valleys, and in particular in the Danube Valley: in winter, fog occurs on average from 4 to 11 days per month.
Snow is quite common everywhere, except in the area of Vienna, where it is more rare.
The coldest temperatures have been recorded after outbreaks of cold air masses coming from Russia: in these cases the temperature can plunge to -15/-20 °C (-4/5 °F), or even lower, either in Vienna and at low altitude. The coldest records are -30 °C (-22 °F) in Innsbruck, Tyrol, 580 metres (1,900 feet) above sea level, and -31 °C (-24 °F) in Salzburg, 435 m (1,400 ft).
Here are the average temperatures in Innsbruck.
Average temperatures - Innsbruck
Min (°C)-7-4-148111312940-4
Max (°C)14111621242624211482
Min (°F)192530394652555448393225
Max (°F)343952617075797570574636

In mountain areas, winter is obviously very cold and snowy, but it is sunnier than in the valleys, because the mountains are above the fog and low clouds layer, therefore they experience an acceptable amount of sunshine hours in this season.

Mountains in Austria

In January and February, the average minimum temperatures range from -5 °C to -9 °C (16 to 23 °F) between 1,200 and 1,800 metres (4,000 and 6,000 feet), and the maximum temperature between -1 °C to +2 °C (30 and 36 °F). In high mountains, above 2,000 metres (6,500 feet), lows range from -8 °C to -14 °C (7 to 18 °F) and highs from -4 °C to -11 °C (12 to 25 °F).
Some areas of Austria are subject to down-slope winds coming from the mountain tops: when the Foehn blows from the south, the temperatures can suddenly increase, and snow can rapidly melt, causing floods and avalanches. In the south, in Carinthia, there's a variant of this wind called Jauk.

Summer is warm or even hot in the Vienna area, with some chance of thunderstorms in the afternoon, while it becomes very rainy in the rest of Austria, because of the Atlantic cold fronts, which can cause unstable weather especially in the afternoon. The thunderstorms usually occur in the afternoon or evening.
Usually the rainiest month in Austria is July: for instance in Salzburg, where it rains almost every second day from May to August, more than 150 mm (6 in) of rain fall in this month, and the total amount of the three summer months (June, July and August) is 465 mm (18 in). On the contrary, the Vienna area is less rainy and a little sunnier.
Here is the average precipitation in Salzburg.
Average precipitation - Salzburg
Prec. (mm)605580851151551601501007585751185

Usually, the temperatures are often pleasantly warm during the day and cool at night: in Vienna the average daily temperature in July is around 20 °C (68 °F), and the maximum temperature is around 25 °C (77 °F) in Vienna and other major cities, but sometimes there may be hot and muggy days, especially in the plain (i.e. in the area of Vienna), with lows above 20 °C (68 °F) and highs above 30 °C (86 °F).
The highest recorded temperatures are 37.7 °C (100 °F) in Linz (East Tyrol), 37.8 °C (100 °F) in Salzburg, 38 °C (100.4 °F) in Feldkirch (Vorarlberg) and 40 °C (104 °F) in Bad Gleichenberg (Styria).

In the mountains, summer becomes cooler with increasing altitude, but it is equally prone to thunderstorms, indeed, the most abundant precipitation is recorded in this area. On average, at mid-mountain altitudes, from 345 to 600 mm (13.5 to 23.5 in) of rain fall in the three summer months, while in the high mountains precipitation can even reach 800 mm (31.5 in), of which 265 mm (10.4 in) in the month of July.
Above 3,000 metres (10,000 ft) on Grossglockner, which is the highest mountain in Austria with its 3,798 metres (12,461 ft), the average temperature is around freezing even in July and August, as we can see from the average temperatures of the Sonnblick Observatory, located at 3,111 metres (10,207 ft) above sea level.
Average temperatures - Grossglockner
Min (°C)-14-14-13-10-5-300-3-6-10-13
Max (°C)-9-10-8-6-12552-2-6-8
Min (°F)77914232732322721149
Max (°F)161418213036414136282118

In the plains and valley bottoms, spring and autumn are quite cold in the periods closer to winter: in March and in November it may freeze and snow: in November were recorded temperatures from -11 °C to -19 °C (-2 to 12 °F), and even -20 °C (-4 °F) in Innsbruck.
The conditions are definitely better in the months of May and September, when usually the temperature is pleasant (although sometimes it can get cold at night) and thunderstorms rarer than in summer. During the warmer days, the temperature can reach or slightly exceed 30 °C (86 °F).
April and October are very cool, sometimes cold: in these months sometimes it can freeze at night, and in April the northerly winds may bring some late snowfalls.
In autumn, in October, mists and fogs become quite frequent.
Spring and autumn in Austria are drier than summer; in autumn, the northern slopes of the Southern Alps are sheltered from the currents usually blowing in this season, bringing heavy rains on the southern side, namely in Italy and Slovenia.

When to go

The best times to visit Vienna and other major cities in Austria are late spring and early autumn, especially the months of May, June and September; to avoid both the period when thunderstorms are more intense, and the possible heat of the plain and low valleys.
The mid-summer period (July-August) is often very rainy and thunderous, and sometimes hot. In hill cities (Salzburg, Innsbruck) it rains a lot more than in Vienna, which however can be hot and muggy. Anyway, all in all summer is not a bad period, especially for those who don't fear the heat.
Winter (December to February) is not the best to visit the cities because it's cold and foggy, and sometimes icy and snowy.

The best time for excursions in the mountains runs from mid-May to September, bearing in mind that in this season, especially in July and August, thunderstorms are frequent in the afternoon. September is quieter, and woods begin to show the spectacular autumn colours.

For skiing, the period March-early April is preferable to the colder months, because it's less cold and the days are longer. Anyway, on high mountains there are ski resorts where you can ski even in summer.

What to pack

In winter: warm clothes, sweater or fleece, down jacket, hat, scarf, gloves, umbrella. For the mountains, mountain outfit, hiking boots.

In summer: light clothes, T-shirt and shorts, but also long pants, jacket and sweatshirt; raincoat or umbrella. For the mountains, hiking shoes, sunscreen and sunglasses; for the highest mountains and glaciers, warm clothes, down jacket, hat.