Six of Friday's nine FL t20 matches were called off as a result of the bad weather sweeping the country.
North Group games between Derbyshire and Nottinghamshire, Leicestershire against Durham and Yorkshire's trip to Lancashire have all been abandoned.
The cancellations mean Notts are guaranteed a quarter-final spot.
Warwickshire v Gloucestershire, Worcestershire v Northants and Welsh Dragons v Somerset were all called off in the Midlands/West/Wales Group.
Derbyshire's home game against Notts was the first to fall after umpire David Millns carried out an early inspection and judged the outfield was too wet for there to be any realistic prospect of play at the County Ground.
"Everybody is disappointed that we aren't able to host one of our showpiece matches of the campaign," said Derbyshire chief executive Simon Storey.
Heavy overnight rain also left the outfield at Grace Road waterlogged, prompting the Foxes' match against Durham to be called off five hours before the scheduled start.
Although Durham cannot finish in the top two in their group, they can book a place in the last eight if they beat Lancashire on Sunday.
The cancellation of Warwickshire's game against Gloucestershire at around 13:45 BST followed Wednesday's abandonment of the one-day international between England and Australia, and means there have been six wash-outs in 10 days of cricket at Edgbaston in barely a month.
Worcestershire's home game against Northants was abandoned at around the same time.
Fixtures at Glamorgan, Surrey, Hampshire and Kent are currently still on.
It means that Warwickshire's, Worcestershire's and Gloucestershire's hopes of progress will be decided in the final round of fixtures on Sunday.