Pakistan had won the second T20I of the four-match series by seven runs on July 31, while the first match too was abandoned because of rain.
Only eight deliveries were possible on Monday (IST) in Guyana, with the West Indies racing to 15/0 in that time. Andre Fletcher hit two sixes in his unbeaten 14 off six, with Chris Gayle making one off two.
Fletcher's second six, smashed back over the head of bowler Mohammad Wasim, came off the final ball of the innings, with a heavy downpour setting in.
The rain continued for the next hour and a half, after which there were hopes of a shortened match but that was ultimately not possible, with one part of the field still waterlogged.
It is the second match of the tour to have been washed out, with the series opener only seeing nine overs of play.
The two teams will next meet on Wednesday (August 4, IST) in the final T20I of the series.
Both sides will be hoping for kinder weather as they prepare for the ICC Men's T20 World Cup 2021 in October-November.