When my son took his American History class, he read to me from the diaries of Lewis and Clark when they wintered on the Oregon coast after coming all the way across the country.  Mostly what they did was complain about the rain:
“Rained again today.”

“Rained all night long and into the morning.”

“Rained all day for the third day in a row.”

Having grown up in western Washington State, I know all about this problem.  Having lived through the last two years in Eastern Oregon, I am intimately familiar with this problem.  We had frozen rain and hail on May 17th.  Wales, climate-wise, is nearly identical to the Pacific Northwest coast.

This was our experience. Here’s Dolbadarn Castle. In the rain.

This is the forecast for Bangor, Wales for the rest of the week:

Five-day forecast (Details)
Tomorrow 19 MayFair	Friday 20 MayShowers	Saturday 21 MayRain	Sunday 22 MayShowers / Clear	Monday 23 MayFair
High: 12° Low: 8°	High: 13° Low: 9°	High: 13° Low: 8°	High: 13° Low: 9°	High: 14° Low: 8°

This is the weather for Cardiff for four days last December:  Light rain; light rain; heavy rain on Saturday; and finally on Sunday, sunny intervals.

Aberystwyth was even better, with: light rain; heavy rain; heavy rain; heavy rain.  It is situated on the west coast of Wales, while Cardiff is in the south.  Conwy has the same forecast as Aberystwyth.

It means that if you are writing a book where the characters are spending any season at all in Wales, it needs to rain.  A  lot.

This is a Mt. Snowdon web cam, with links to other web cams in Gwynedd.  Delightfully, during the summer, it is light in Wales 14-16 hours a day, so the eight hours it is off from my time zone makes little difference:  http://www.bbc.co.uk/wales/northwest/sites/webcams//pages/snowdon.shtml