The biggest factor is the supression of cumulus cloud in the spring,
summer and early autumn through regular sea breezes. Often the sky is
cloudless here whereas just a few kilometres inland cumulus builds up
and there may even be showers/thunder, especially in the spring.


Nick Gardner
Otter Valley (and with beavers too), Devon
20 m amsl
http://www.ottervalley.co.uk

The affect of this in Spring/Summer is so great it more than compensates (in a normal year - 2012 was a bit of an exception) for Autumn/Winter when onshore coasts tend to be cloudier.

This is well demonstrated by http://www.metoffice.gov.uk/climate/...aries/anomacts

Select Annual, Actual sunshine and take a look at the last 5 or 6 years.

Every year (except 2012) shows the sunniest areas in the SW to be Scilly, Land's End peninsula & north Cornwall, and the area from about where you are Nick, to Portland. East of this the whole south coast does very well, with the sunniest bits where it's relatively exposed, like the Isle of Wight & Eastbourne.

In the south west, where the prevailing wind is offshore, such as in Torbay, it is normally cloudier. (Not what you might assume by the repeated forecasts of more sunshine to the east of high ground)

It's a shame there is no sunshine recorded out at Sennen, I'm confident that area is the sunniest in Cornwall, nothing land around (apart from to the E-NE) to generate Cu. The sunshine's often unbroken in Summer when there's a 50% cloud cover even in Penzance. East Cornwall is much cloudier, especially to the SE of Bodmin Moor.

Graham
Penzance