In the rain the bare dark trees reflect the streetlights behind them on their wet branches. The light, it appears, shines through in cones. When you look at a streetlight in the dark you’ll see a triangle of light coming from it, but it’s really a cone, as you can tell by the circle you see from planes.
I’m not sure why light behaves this way, and I don’t really care, but it is interesting to see the effect on the wet, dark trees as it shines through them at an angle (maybe it has to do with the eye being round that sees it). The effect is of making the branches seem to be wrapping around the light. The light only shines on the parts of the branch inside the cone, and the rest is black. And it’s like giant gleaming spider webs.