No play was possible in the Vitality Blast South Group match between Somerset and Glamorgan at the Cooper Associates County Ground, Taunton.
Rain was already falling ahead of the scheduled 7pm start, delaying the toss and announcement of the teams.
The weather worsened as the evening progressed, forcing umpires Nigel Llong and Steve O'Shaughnessy to abandon any prospect of play at 8.25pm.
The abandonment left Somerset on four points from five games and Glamorgan on five from six matches, both with plenty of work to do to qualify from the group.