Silesia Geography & Climate

Silesia sits in southern Poland on the upper Oder and Vistula basins, and its geology is the reason for everything else about it.

The coalfield

The Upper Silesian Coal Basin is one of the largest hard-coal deposits in Europe, and it lies under a plateau at 250 to 350 metres. That coal produced the densest urban agglomeration in Poland — a conurbation of a dozen cities running into one another with around two million people, which grew in the nineteenth century as a single industrial organism rather than as separate towns.

Mining subsidence

Two centuries of extraction have left the ground unstable in places: subsidence hollows, tilted buildings, and artificial lakes formed where the surface has sunk and filled with water. Some of these are now recreation areas.

The Jura

North-east of the coalfield, the Krakow-Czestochowa Upland is a belt of Jurassic limestone eroded into white crags, caves and isolated towers, with castle ruins along its length. Quite unlike anything around it.

The Beskids

In the south the land rises into the Silesian and Zywiec Beskids, forested Carpathian foothills reaching around 1,200 metres at Skrzyczne and Barania Gora, where the Vistula rises.

Where the Vistula begins

Poland’s great river rises on the slopes of Barania Gora in the Silesian Beskids as two small streams, the White and Black Vistula, which join at Wisla town. From there it runs a thousand kilometres north to the Baltic through Krakow, Warsaw and Gdansk. That a river so central to the country starts in its most industrial region is a neat accident of geography, and the source is marked and walkable.

Rivers and air

The Oder drains the west and the Vistula the east. The basin shape of the coalfield traps cold air in winter, which is central to the region’s smog problem.

Silesia has a temperate continental climate, moderated slightly in the south by the mountains and dominated in winter by a problem that is more consequential than the weather itself.

Summer

June to August averages 23 to 26°C, with heatwaves increasingly reaching the low thirties. Thunderstorms are frequent, and this is the pleasant half of the year.

Winter

December to February hovers around freezing, with cold snaps to −15°C. Snow is intermittent in the lowlands and reliable in the Beskids, which have a proper ski season from December to March.

The smog

This is the defining seasonal fact. On cold, still winter days, temperature inversions trap air in the shallow basin of the coalfield, and emissions from coal and solid fuel burned in old domestic stoves accumulate. Silesian towns have repeatedly recorded the worst air quality in the European Union, with particulate readings many times the safe limit — a few hours outdoors on a bad day has been compared to smoking a packet of cigarettes. Poland has been found in breach of EU air quality law over it, and replacement of household boilers is underway but incomplete.

The practical advice: check the air quality index, which is published and widely used, and reconsider a winter visit if you have asthma or a heart condition.

Why the basin traps it

The coalfield sits in a shallow depression, and on a still, cold night a layer of warmer air settles above the colder air at ground level. That inversion acts as a lid: nothing disperses, and the emissions from tens of thousands of domestic stoves accumulate under it for as long as the weather stays calm. It is the same mechanism that afflicts Krakow, and it is why wind — rather than any reduction in emissions on the day — is what clears the air.

Spring and autumn

May and September are the best months — mild, clear, and with the air clean.