Aosta Geography & Climate

Aosta sits in the middle of a valley that is closed at the top and walled on both sides, and the arrangement has decided everything about it.

The valley

The Dora Baltea runs the length of the region from the glaciers below Mont Blanc down to the Piedmont plain, and Aosta occupies the widest flat stretch of it, where the Buthier comes in from the north. It is the only place in the region with room for a city.

Four massifs

The valley is ringed by Mont Blanc at 4,808 metres, the Matterhorn, Monte Rosa and Gran Paradiso — the highest concentration of high ground in the Alps, and the reason the side valleys are so deep and so distinct from one another.

The passes

Two of the oldest Alpine crossings leave from here: the Great St Bernard to Switzerland and the Little St Bernard to France. The city exists because Rome wanted to control both.

A dry valley

The surrounding walls keep out most weather, and the central valley is unusually dry, with irrigation channels — ru — cut along the hillsides since the medieval period to bring meltwater to the fields.

The highest vines in Europe

The south-facing slopes carry terraced vineyards up to about 1,200 metres, some of them on ungrafted pre-phylloxera rootstock, which is genuinely rare.

Glaciers in retreat

The ice fields that feed the Dora Baltea are shrinking measurably from year to year, and the difference between an old photograph and the same view now is one of the clearest things a visitor can see here.

Gran Paradiso

South of the city the ground rises into Italy's first national park, created in 1922 out of a royal hunting reserve to save the Alpine ibex from extinction.

Aosta has one of the driest and sunniest climates in the Alps, because the mountains around it take the weather first.

Rain shadow

The high ranges on every side intercept most of the precipitation, and the central valley receives well under 600 millimetres a year — one of the lowest totals in northern Italy, and the reason the irrigation channels exist.

Winter

Winter is cold and clear, with highs around 6°C, hard night frost and a great deal of sun. Snow falls in the city several times a season and does not usually last long on the valley floor, while the side valleys are under it for months.

Summer

Summer is warm and dry, with highs around 28°C, cool nights and very little humidity. It is the most comfortable summer of any Italian regional capital.

Big daily swings

The dry air and the altitude produce large differences between day and night in every season, which is worth planning clothes around.

Spring and autumn

Spring is late and abrupt; autumn is long, clear and the best walking of the year, with the larches turning through October.

The mountain is a different country

Conditions at 2,500 metres in the side valleys bear no relation to the city; snow can close passes in June and September.

Sun as a resource

The number of clear days here is high enough that the valley has historically counted on it: the terraced vineyards, the drying of meat and the siting of villages on south-facing shoulders all depend on sun rather than on warmth.

What to bring

Layers, sun protection at any season, and real equipment if you go up.