The Lakes do sometimes get snow into April so you really need to be prepared for anything. People there hike all 4 seasons though so as long as you have the right gear you can still go! I've hiked there many times in spring, summer, and fall and you just have to be prepared with water-resistant boots, jacket, hood, and hiking pants. If you get there and don't have something you have George Fischer as well as a number of other outdoor gear stores in Keswick and several other towns.
You really can't avoid rain at any time of the year there. It rains on a fairly regular basis but that's why it is so very beautiful...and when the sun comes out, wow!! It's worth putting up with some bad weather just for those days.
There are some great Facebook pages for fans of the Lake District so that you can get an idea of what it's like...there are many, many pictures posted every day and it's fun for getting ideas of where to go next.
I Love the Lake District - mostly residents of the area and visiting fans! It's fun to watch the seasons go by.
Lakeland, Molly & Afar - run by a National Trust ranger and his dog Molly. Lots of pics of people's dogs but lots of the lakes too. He works the Buttermere area so there are many pics from around there.