As long as there is no lightening, the rides still go! If there is lightening, the outside rides must wait 20 minutes after each flash before starting up again.
On our Grand Gathering this summer all 13 of us (from 12 year old cousin to 70 year old Grandma) went on BTMRR and just as the we starting clicking up the mountain, we heard the skies open up in down pour. This was during Tropical Storm Alberto, so some of us had ponchos on anyway. I put my hood up, held it tight around my face and off we went!! It was absolutely hysterical.
All of us so close together on the train and knowing there was nothing we could do about the deluge...I had never laughed so hard in my life!! My beautiful aunt's mascara had smeared from her eyes down her face, in her hair and onto her poncho. Then we decided since we were absolutely soaked anyway (btw, the poncho hood did *nothing* to help
) we went on SM. When we went through the line the CM asked how many there were, we said 10 (Grandma & a few others bowed out of this one) he said "are you serious?" "yep!" and he allowed all 10 of us to ride in one log! 3 and 3 in the front 2, 2 and 2 in back.
All this to say, heavy rain + thrill rides + Disney magic = memories your family will relive every time you get together!!
Have fun!!