elm, as well as evergreen, coniferous trees of the wet alpine zone. Orchids are common and rare varieties of orchids are featured in flower shows in the city. Bamboo is also abundant. In the lower reaches of the town, the vegetation gradually changes from alpine to temperate deciduous and subtropical. Flowers such as sunflower, marigold, poinsettia and others bloom, especially in November and December. Climate Gangtok has a monsoon-influenced subtropical highland climate (Köppen: Cwb). Because of its elevation and sheltered environment, Gangtok enjoys a mild, temperate climate all year round. Like most Himalayan towns, Gangtok has five seasons: summer, monsoons, autumn, winter and spring. Temperatures range from an average maximum of in summertime to an average minimum of in winter. Summers (lasting from late April to May) are mild, with maximum temperatures rarely crossing . The monsoon season from June to September is characterised by intense torrential rains, often causing landslides that block Gangtok's land access to the rest of the country. Rainfall starts to rise from pre-monsoon in May and peaks during the monsoon, with July recording the highest monthly average of . In winter temperature averages between and . Snowfall is rare and in recent times, Gangtok has received snow only in 1990, 2004, 2005 and 2020. Temperatures below freezing are also rare. During this season the weather can be unstable and change abruptly from bright sunshine and clear skies to heavy rain within a couple of hours. During spring and autumn the weather is generally sunny and mild. Owing to its elevation, Gangtok is often enveloped in fog during the monsoon and winter months. Economy Gangtok is the main base for Sikkim tourism. Summer and spring seasons are the most popular tourist seasons. Many of Gangtok's residents are employed directly and indirectly in the tourism industry, with many residents owning and working in hotels and restaurants. Mahatma Gandhi Marg and Lal Market are prominent business areas and tourist spots in Gangtok. Ecotourism has emerged as an important economic activity in the region which includes trekking, mountaineering, river rafting and other nature oriented activities. An estimated 351,000 tourists visited Sikkim in 2007, generating revenue of about . The Nathula Pass, located about from Gangtok, used to be the primary route of the wool, fur and spice trade with Tibet and spurred economic growth for Gangtok till the mid-20th century. In 1962, after the border was closed during the