I have six ducks. With the first four I worried about rain. We have had a lousy, wet summer in the Pacific Northwest. My quip now is, "the only ones happy with this weather are my ducks." They have loved this summer.....because it has poured down rain more than not. With my second group, I have let them do as they please, they just love that rain. Even let them out much earlier than did the prior group. (I tended to put them in the duck house when it rained, silly me.) Once they show signs of having water proof feathers, the water is their favorite activity - next to mud. We learn as we go along....ducks are happy, so let them be.
Lightening would cause a bit of concern though.
We just introduced the two new ducklings to the flock in the last week. Last night 5 ducks were outside in the pen, and one new duck disappeared inside the house. Scared the heck out of me. Was convinced the "old" ducks must have attacked her (even though the pushing and shoving stage seems to have passed). Took a hasty trip to the duck house. Only to find the 6th duck sitting just inside the duck house door watching the rest of the group, happy as a clam. (Husband told me he hopes I quit worrying about them so much soon, because they are just farm animals... Apparently, he's not as attached to the ducks as much as our dachshunds!)