If you're new to this "living in the UK" thing (like within the past 6 weeks), you may think that A) it rains every day and the sun never shines and that B) the fact that it's been the wettest spring on record is the only reason British people talk about the weather all.the.time.
Allow me to clear up a few things (and lazily recycle a post from ages ago):
A) It really doesn't rain all the time - see this old, but popular, post for "proof"
B) Unfortunately, the unusual weather pattern and persistant rain or even the previous drought conditions aren't the reason British people insist on talking about the weather at any opportunity. This happens all the time, no matter the weather. My suggestion - learn some meteorology phrases then learn to exhale deeply and say "it's so lovely out there" when the sun shines and roll with the punches.
Oh, and if you are feeling a bit of springtime SAD, the Telegraph has put together a slideshow thingie that basically tells that if you want sunnier days, move to the South. Duh.