[7] The close proximity of Sussex to the Continent of Europe, results in cold spells in winter and hot, humid weather in summer.

[7] The climate of the coastal districts is strongly influenced by the sea, which, because of its tendency to warm up slower than land, can result in cooler temperatures than inland in the summer.

[8] From the summit of the Downs the hilly country observed on the northern side is occupied mainly by the Hastings Beds and the Weald Clay; at the foot of the escarpment lie the Gault and Upper Greensand, while between these formations and the Wealden rocks there is an elevated ridge of ground formed by the Lower Greensand.

Superficial deposits cover much of the coastal plain; these include glacial deposits with large boulders, raised beaches, brick earth and gravels, marine and estuarine, and the interesting Lower chalk or Coombe rock, formerly known as Elephant Beds, a coarse rubble of chalk waste formed late in the Glacial period, well exposed in the cliff at Black Rock east of Brighton, where it rests on a raised beach.

The southern side of the South Downs are deeply notched by dry valleys or coombes, which frequently end in cirques near the northern escarpment.

Devil's Dyke is the most famous and remarkable of all the chalk dry valleys and is frequently cited as the type example.

Bordering the outcrop of the Weald Clay is the Lower Greensand Group; it appears a little north of Eastbourne and passes thence through Ringmer, Storrington, Pulborough, Petworth, Midhurst and Linchmere.

The Wealden iron industry was established before the Roman invasion and was superseded in the 18th century by coal areas of Wales and northern England.

There remains a long-established deep-mining operation centred on the High Weald village of Brightling, the country's largest resource of calcium sulphate or gypsum.

[10] In the 21st century, there has been oil drilling at Singleton, in the South Downs north of Chichester as well as Baxters Copse and Storrington in the Low Weald.

[11][12] With some controversy locally, hydraulic fracturing of shale gas has been proposed to be taken from the Low Weald near Balcombe close to the Brighton Main Line railway.

The beaches along the coast vary from sandy to shingle: that factor, together with the mild climate of the coast, sheltered by the hills from north and east winds, has resulted in the growth of numerous resort towns, of which the most popular are (east to west) Brighton, Shoreham-by-Sea, Worthing, Littlehampton and Bognor Regis.

They run east for some 50 miles (80 km), gradually approaching the coast, and terminating in the bold promontory of Beachy Head near Eastbourne.

The northern arm reaches the sea at Folkestone (in Kent); the southern at Fairlight Down east of Hastings.

Within the Weald lies Sussex's highest point, the pine-clad Black Down, close to the Surrey border at 280 metres (920 ft).

[21] Another high point is in the part called Forest Ridges: a height of 242 metres (794 ft) is reached at Beacon Hill[20] in the neighbourhood of Crowborough.

At Brighton the coastal plain is replaced by chalk cliffs which culminate in the Seven Sisters and the promontory of Beachy Head.

West of Hastings at Bulverhythe and periodically exposed lies the remains of a submerged submarine forest, known locally as 'Moon Shore'.

Sussex's offshore environment includes such varied features as the Shoal of the Lead 8 kilometres (5.0 mi) south of Selsey Bill where the seabed drops steeply to 67 metres (220 ft) causing strong underwater cascades, a feature which may be unique to the British Isles.

The Mixon Hole is a clay cliff which extends some 30 metres (98 ft) down[26] and contains unusual plant assemblages and a rare combination of species which only occur there,[26] while the Worthing Lumps are considered some of Europe's finest chalk reefs.

In 2014 UNESCO made Brighton and Hove and the area between the rivers Adur and Ouse the world's first urban biosphere reserve.

Good examples of near-natural beech woodland can be found at The Mens and Ebernoe Common[37] in the Sussex Weald.

[42] The UK's largest population of feral wild boar are in the Weald with around 200-300 individuals living close near the East Sussex-Kent border.

[49][50] It is now a breeding hotspot for purple emperor butterflies, turtle doves and 2 per cent of the UK's population of nightingales.

[54][55] Grant Allen argued that until the modern era, Sussex was effectively isolated from the rest of England by its geography.

[56] Before drainage and reclamation, Sussex was separated from Hampshire to the west by great tidal flats and swamps around Havant and Hayling Island.

The town of Boulogne-sur-Mer in Pas de Calais, France, lies approximately 38 miles (61 km) to the east of Camber Sands.

In 1997, Brighton and Hove became a self-administered unitary authority; it was granted city status in 2000, whilst remaining part of the ceremonial county of East Sussex.

[3][4] Both titles are honorary and there currently little administration organised on a Sussex-wide basis, since the creation of county councils for East and West Sussex in 1889.

[71] According to Mark Gardiner, the different nature of Sussex's borders with Kent and with Surrey indicate two separate and larger-scale agreements and may represent boundaries of Roman civitates or Iron Age kingdoms.