Warwickshire ended a stop-start Twenty20 contest in Cardiff with their fifth victory of an unbeaten campaign.
The match against hosts Glamorgan began nearly an hour late, with each side expecting to face 15 overs.
After Warwickshire had batted for 10 overs to be 73-2, the rain struck, and just one more over was possible, bowled by Ryan Watkins, with 21 runs added.
Glamorgan were set 83 to win off nine overs, but despite 12 coming off the first, they ended 10 short on 73-6.
Warwickshire had been indebted to a partnership worth 83 between Darren Maddy and Tim Ambrose - the latter scoring his 42 off just 25 balls before falling to Watkins in the final over.
After being 7-2 in the second over, it had been a fine recovery by the Bears to end on 94-3.
The Dragons began their chase at 2145 BST, Robert Croft and Richard Grant giving them a good start,
But James Anyon struck twice in his first over, with both Paul Harris and Heath Streak also on the money.
Three Mark Wallace sixes in one Tim Groenewald over briefly brought Glamorgan back into the contest.
But Harris struck again, finishing with a fine 2-7 off his two overs, and the Welsh county could not reply.