England, Bristol is one of the warmest cities in the UK with a mean annual temperature of approximately . It is among the sunniest, with 1,541–1,885hours of sunshine per year. Although the city is partially sheltered by the Mendip Hills, it is exposed to the Severn Estuary and the Bristol Channel. Annual rainfall increases from north to south, with totals north of the Avon in the range and south of the river. Rain is fairly evenly distributed throughout the year, with autumn and winter the wetter seasons. The Atlantic Ocean influences Bristol's weather, keeping its average temperature above freezing throughout the year, but winter frosts are frequent and snow occasionally falls from early November to late April. Summers are warm and drier, with variable sunshine, rain and clouds, and spring weather is unsettled. The weather stations nearest Bristol for which long-term climate data are available are Long Ashton (about south west of the city centre) and Bristol Weather Station, in the city centre. Data collection at these locations ended in 2002 and 2001, respectively, and Filton Airfield is currently the nearest weather station to the city. Temperatures at Long Ashton from 1959 to 2002 ranged from in July 1976 to in January 1982. Monthly high temperatures since 2002 at Filton exceeding those recorded at Long Ashton include in April 2003, in July 2006 and in October 2011. The lowest recent temperature at Filton was in December 2010. Although large cities in general experience an urban heat island effect, with warmer temperatures than their surrounding rural areas, this phenomenon is minimal in Bristol. Environment Bristol was ranked as Britain's most sustainable city (based on its environmental performance, quality of life, future-proofing and approaches to climate change, recycling and biodiversity), topping environmental charity Forum for the Future's 2008 Sustainable Cities Index. Local initiatives include Sustrans (creators of the National Cycle Network, founded as Cyclebag in 1977) and Resourcesaver, a non-profit business established in 1988 by Avon Friends of the Earth. In 2014 The Sunday Times named it as the best city in Britain in which to live. The city received the 2015 European Green Capital Award, becoming the first UK city to receive this award. In 2019 Bristol City Council voted in favour of banning all privately owned diesel cars from the city centre. Since then, the plans have been revised in favour of a clean air zone whereby older and more