Most of the bus services in that part of Lakeland are operated by Stagecoach, and you can find details of all their summer services here: https://www.stagecoachbus.com/promos...ct-this-summer. They do a PDF and printed Lakeland guide with all the bus timetables in it.

If you are intending to stay around Low Lorton, then making Keswick your base might be the best bet, although it does get busy in summer. The best station for Keswick and the North Lakes is Penrith, as the X4/X5 bus stops outside the railway station. It's possible to get to Keswick from Kendal and Windermere on the 555 bus too, which also runs every 30 minutes during the day, although it takes quite a bit longer.

Daytime buses around Keswick tend to be OK- the bus from Keswick to Low Lorton runs every two hours during the day, which is hardly sparse, but does require organisation- but after about 5pm you're largely reliant on taxis.

As for weather, it's often said up here that if you can see the fells it's about to rain and if you can't it already is raining. And if you don't like the weather it doesn't matter because it'll change in twenty minutes. Pack layers, it can be nice and warm and sunny during the day but by the evening it will be chilly.

I love this part of the world. I'm sure you will too.