The variation in length of day throughout the year means that the duration of sunshine shows a marked annual variation. On average, December is the month with the least sunshine and July is the sunniest. In general sunshine duration decreases with increasing latitude although proximity to the coast also plays an important role. Subsidence associated with high pressure reduces cloud cover and in spring and summer, when the sea is cool relative to the land, there is little convective cloud over the sea. Coastal areas are then favoured by high sunshine amounts, whereas convective cloud often forms inland.
The graphs show the average monthly sunshine totals for Waddington and Lowestoft, together with the highest and lowest totals recorded in the stated periods. Compared to coastal resorts in SW England, the Norfolk coast has about 10% less sunshine hours throughout the year. Low cloud from the North Sea can affect the coast especially in spring and summer. Across the region, annual averages range from less than 1450 hours over much of Lincolnshire and East Yorkshire to over 1550 hours in eastern Suffolk and Essex. For comparison, the Channel Islands are the sunniest place in the UK with some locations exceeding 1900 hours per year and the Shetland Islands the least sunny with an average of only 1100 hours per year.
The highest known monthly total in the region is 318.1 hours recorded at Cromer in July 1976. The highest UK monthly total is 383.9 hours in July 1911 at Eastbourne. In the dullest winter months less than 20 hours have been recorded on occasion. At Westminster in Central London there were no hours recorded during December 1890.
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