The game at Grace Road was due to get under way at 18:30 BST.
But umpires Russell Evans and Rob Bailey ruled the ground was unfit for play after a late-morning inspection.
The two clubs were also hit by the weather on Wednesday when their One-Day Cup match at New Road was rained off.
A statement on the club website said: "Aylestone was affected by flash flooding on Tuesday and the Fischer County Ground resembled a lake with the water subsequently gathering in the far corner of the ground.
"Further rain has fallen either side of that particular deluge and although the club brought in heaters to try to dry everywhere out, conditions remain sodden and unfit."
Worcestershire will have Moeen Ali available for Saturday afternoon's home T20 Blast game against Nottinghamshire, for whom fellow England Test player Alex Hales is scheduled to appear.
"It's good when you've got England players playing," said Worcestershire director of cricket Steve Rhodes. "It is a big bonus having Mo available.
"It is a sensible thing to do by the ECB. They want our Blast tournament to have good exposure and become a really good domestic tournament.
"Just as in the Caribbean Premier League, Big Bash and IPL, a lot of the home international players play in those tournaments."
Worcestershire will give fitness tests to skipper Daryl Mitchell and paceman Matt Henry, who have both been sidelined with rib injuries.

Bashir Naderi, 20, has lived in Wales for 10 years, after his mother paid traffickers to bring him to the UK.
His deportation was temporarily halted by a judge hours before he was due to board the plane in October and a 14,000-signature petition was handed into the Home Office in January.
But girlfriend Nicole Cooper said they are "devastated" his leave to remain in the UK has been refused.
She added their solicitor delivered the news on Wednesday but the couple are still waiting to see the Home Office documents.
The Home Office said it did not comment on individual cases.
"I was in work and my mum rang me at 3pm to say the solicitor had contacted Bash," Miss Cooper told BBC Wales.
"We had a call from the solicitor giving more detail, she was in London. It was that he hadn't been granted leave by the Home Office. We're waiting to see the document she received.
"Bash's solicitor is still fighting this, there are grounds for another appeal."
Mr Naderi fled from Afghanistan at the age of 10 after his father was killed by the Taliban.
He went to school in Cardiff and speaks with a local accent.
"He's not taken it well," added Miss Cooper. "He is devastated and has been upset about the whole thing.
"We genuinely weren't expecting it, we thought we had a good chance."
Among the thousands of people to sign the petition were Welsh singers Charlotte Church and Cerys Matthews, as well as local MP Jo Stevens.

For six months the International Space Station (ISS) will be his home.
The ISS was launched back in 1998 and astronauts have been living on board ever since.
It's an important place to carry out tests and research that will help future space missions to places like the Moon and Mars.
Take a look at the ISS in numbers:
Friday's T20 Blast match between Leicestershire and Worcestershire was called off almost seven hours before the scheduled start after heavy rain left the outfield "resembling a lake".
[NEXT_CONCEPT]
A bid to stop a Cardiff man from being deported to Afghanistan has failed.
[NEXT_CONCEPT]
Major Tim Peake is getting ready to blast into space to complete his first mission.