The best months to visit Guernsey are August and July. See monthly temperatures, rainfall and rain days (1991–2020 averages) to plan your trip.
Average daytime high and monthly rainfall in Guernsey: January 10°C / 99mm; February 11°C / 76mm; March 10°C / 60mm; April 11°C / 51mm; May 13°C / 45mm; June 15°C / 43mm; July 17°C / 37mm; August 18°C / 52mm; September 17°C / 58mm; October 16°C / 110mm; November 14°C / 123mm; December 12°C / 122mm.