South-west England

The number of hours of bright sunshine is controlled by the length of day and by cloudiness. The day is shortest in December and longest in June, and so in general December is the dullest month and June the sunniest. The south-west of England has a favoured location with respect to the Azores high pressure when it extends its influence north-eastwards towards the UK, particularly in summer. Subsidence associated with high pressure reduces cloud cover, and in spring and summer when the sea is cool relative to the air there is little convective cloud over the sea. Coastal areas are then favoured by high sunshine amounts. Convective cloud often forms inland, especially near hills, and acts to reduce sunshine amounts.

Coastal areas in the south-west have average annual sunshine totals above 1600 hours, the south (English Channel) coast being more favoured than the north (Bristol Channel) coast. Compare this with the 1100 hours per year recorded on the Shetland Islands. Inland the annual sunshine totals are mainly between 1400 and 1600 hours. Table 1 shows monthly means for Teignmouth, a coastal site in south Devon, and Yeovilton, an inland site in Somerset.

Map of Annual mean duration of sunshine hours (1971-2000)

Table 1. Monthly mean hours of bright sunshine for Teignmouth and Yeovilton for 1971-2000 and some recorded extremes.

(*) For period 1926-2003, some years missing.

(**) For period 1983-2003.

Table 1 shows that the coastal site at Teignmouth has more sunshine than Yeovilton for all months. Both places have most sun in July (with May, June and August close behind), and least in December. The highest known monthly sunshine totals in the area are for June 1925, when 334.8 hours were recorded at Long Ashton, and 381.7 at Pendennis Point in Cornwall. The highest UK monthly total is 383.9 for July 1911 at Eastbourne, only a few hours above the Cornwall record. In the dullest winter months less than 20 hours have been recorded on occasion.

Days with no sun at all in June are relatively rare and most places usually record only one or two days. However, there were seven sunless days in June 1977 at Teignmouth. Sunless days are more common in December, and five or six days are the minimum to be expected. There were, however, 20 days without sun at Yeovilton in December 1998 and 18 at Teignmouth for the same month in 1995.

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