Lightening & Thunder? No, too dangerous! If it calms down and still raining, then you might run them in and fasten them up. I shut all my chickens up just before dark. They usually beat me to it and are snug on their roosts when I come to fasten them in.
when my girls were still young - they were out in the rain and I panicked so like a dummy I ran out there to and chased them all back into thier little temp coop, as soon as I got them locked up and got into dry clothes it stopped raining -- sun came out so I let them back out within a few minutes it started to rain again and the girls would NOT go back in thier coop - so I gave up - they love playing in the rain and jumping in the mud puddles.
Yea it has been raining here all day too. My girls were all out in the rain all day. They finally went in just before dark. It doesn't seem to bother them any even when the rain turned to snow the back to rain.