The United Kingdom experiences a temperate maritime climate with cool winters and warm summers. Most of the country falls within USDA hardiness zone 9, although some areas dip into zone 8 or reach zone 10. This zone is characterized by minimum winter temperatures ranging from -6.7°C to -3.9°C.
Most of the United Kingdom is located in USDA Zone 9, although climates as chilly as Zone 8 or as mild as Zone 10 aren’t uncommon. Some specific locations in the UK that fall within Zone 9 include Aberdeen, Aberystwyth, Ballycastle, Ballymena, Barnet, Barnsley, Barrow-in-Furness, Barry, Basildon, Bath, Becontree, Belfast, Berwick-upon-Tweed, Bexhill, Bexley, Birmingham, Blackburn, Blackpool, Bolton, Boston, Bournemouth, Bradford, Brent, Brighton, Bristol, Bromley, Bryher, Caernarfon, Cambridge, Camden, Campbeltown, Cardiff, Carlisle, Chelmsford, Coventry, Craigavon, Cromer, Croydon, Darlington, Derby, Derry, Dorchester, Dover, Dudley, Dumfries, Dundee, Durham, Ealing, Eastbourne, Easton, Edinburgh, Enfield, Exeter, Falmouth, Filey, Fort William, Freshwater, Glasgow, Gloucester, Grantham, Greenock.
It's important to remember that these zones are general classifications. Specific locations within the UK can have microclimates that differ slightly from the overall zone designation.