Unlike many of the academic bloggers I read, rain does not make me want to settle down and do a lot of work. Rain makes me want to doze off again, lulled by the drops on the roof; get up late; bake cookies and eat them; read a novel, preferably one set in England or Scotland, to go with the ambience; take a nap; have a cup of tea and read a bit more; bake something else for dinner; go to bed early. If it goes on for days, then I lose the cozy feeling and just get depressed.
Sunlight, however, makes me bounce out of bed and head to my desk.
This is a learned reaction. Where I grew up, I had allergies pretty much year round, but they were worst in late spring and early summer. By my mid-teens, I had learned that on a sunny, bright, breezy day---when my peers wanted to ditch class in favor of swimming, cycling, picnicking or just making out on the lawn---the best place for me was a climate-controlled building whose windows did not open. That is, the library. Windows were good---I did like to see the sunlight, flowers, grass and trees. But I had to enjoy them from inside.
Later on, better allergy meds were invented. But I still have the sun > library reaction. I don't know why I turn to such a slug in the rain, unless it's just that rain is the best white noise ever.