The umpires have taken another look and decided that it will not be possible to begin even a five-overs-a-side game today.
The quarter-final between Somerset and Notts Outlaws will now be played on Bank Holiday Monday, starting at 13:00 BST, and the weather forecast looks much better.
We will be here again to provide you with full coverage from about 12:40 BST.
Post update
Looks like the umpires' watches are a little fast.....inspection was due at 16:00 BST...
It will be a reduced-overs match between Somerset and Notts Outlaws if we get any play today.
But is it right that a quarter-final is decided in that way when there is a reserve day available?
Tweet us your thoughts to #bbccricket. Here's one view.
From Simon Dolley: "Absolutely ridiculous that after 14 matches the semi final places could be decided by a 5 over match, even though they could come back tomorrow and play a full twenty over match."
Post update
While we wait for the 16:00 BST inspection at Taunton, here are some key moments from Worcestershire's win over Gloucestershire in Saturday's quarter-final.
Video content
This content is currently not available
Post update
So that is the current situation in Taunton.
Our BBC Radio 5 live sports extra commentary team are continuing to broadcast, so please click the link at the top of the page to tune in to the chat about a range of cricket issues.
We will resume updates on this page when we have some more information for you.
Umpires plan inspection
Somerset v Notts Outlaws - T20 Blast quarter-final
The umpires have taken a quick look and will carry out another inspection at 16:00 BST.
It seems therefore that it will not be possible for a full 20-over game to be played.
Somerset made it clear this morning that "every avenue" would be pursued to try and play some sort of a game today.
T20 Blast matches must be a minimum of five overs per side, and as we told you a few minutes ago (see 14:43 entry), the latest such a game could start is 17:58 BST.
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Post update
...but are conditions taking a slight turn for the better?
This morning's forecast for Taunton from the BBC Weather website did not look promising, and has proved spot-on so far with persistent rain in the area for the past few hours.
Play can start as late at 16:00 for a full 20-overs a side contest, but after that the number of overs will be reduced.
The umpires have confirmed that the latest possible start time for a minimum five-over game would be 17:58 BST.
In the event of no play being possible today, the match will take place on Bank Holiday Monday instead - and if that is washed out, there will be a bowl out at Taunton's indoor school.
BBC WeatherCopyright: BBC Weather
Good afternoon
We know three of the teams who will be at T20 Blast Finals Day.
But who will be joining Lancashire Lightning, Sussex Sharks and Worcestershire Rapids at Edgbaston on 15 September?
Will it be 2017 winners Notts Outlaws, who are trophy hunting again in the game's shortest format, or can Somerset - the only team remaining without a nickname - reach the semi-finals for the first time since 2012?
You're in the right place to find out - but there is rain at Taunton, so how much, if any, cricket will we see?
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All times stated are UK
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Latest PostPlay abandoned at Taunton
The umpires have taken another look and decided that it will not be possible to begin even a five-overs-a-side game today.
The quarter-final between Somerset and Notts Outlaws will now be played on Bank Holiday Monday, starting at 13:00 BST, and the weather forecast looks much better.
We will be here again to provide you with full coverage from about 12:40 BST.
Post update
Looks like the umpires' watches are a little fast.....inspection was due at 16:00 BST...
Get Involved
Somerset v Nottinghamshire - inspection 16:00 BST
It will be a reduced-overs match between Somerset and Notts Outlaws if we get any play today.
But is it right that a quarter-final is decided in that way when there is a reserve day available?
Tweet us your thoughts to #bbccricket. Here's one view.
From Simon Dolley: "Absolutely ridiculous that after 14 matches the semi final places could be decided by a 5 over match, even though they could come back tomorrow and play a full twenty over match."
Post update
While we wait for the 16:00 BST inspection at Taunton, here are some key moments from Worcestershire's win over Gloucestershire in Saturday's quarter-final.
Video content
Post update
So that is the current situation in Taunton.
Our BBC Radio 5 live sports extra commentary team are continuing to broadcast, so please click the link at the top of the page to tune in to the chat about a range of cricket issues.
We will resume updates on this page when we have some more information for you.
Umpires plan inspection
Somerset v Notts Outlaws - T20 Blast quarter-final
The umpires have taken a quick look and will carry out another inspection at 16:00 BST.
It seems therefore that it will not be possible for a full 20-over game to be played.
Somerset made it clear this morning that "every avenue" would be pursued to try and play some sort of a game today.
T20 Blast matches must be a minimum of five overs per side, and as we told you a few minutes ago (see 14:43 entry), the latest such a game could start is 17:58 BST.
Post update
...but are conditions taking a slight turn for the better?
Post update
It was a soggy scene at Taunton about 45 minutes ago....
Weather outlook
Somerset v Notts Outlaws - start delayed
This morning's forecast for Taunton from the BBC Weather website did not look promising, and has proved spot-on so far with persistent rain in the area for the past few hours.
Play can start as late at 16:00 for a full 20-overs a side contest, but after that the number of overs will be reduced.
The umpires have confirmed that the latest possible start time for a minimum five-over game would be 17:58 BST.
In the event of no play being possible today, the match will take place on Bank Holiday Monday instead - and if that is washed out, there will be a bowl out at Taunton's indoor school.
Good afternoon
We know three of the teams who will be at T20 Blast Finals Day.
But who will be joining Lancashire Lightning, Sussex Sharks and Worcestershire Rapids at Edgbaston on 15 September?
Will it be 2017 winners Notts Outlaws, who are trophy hunting again in the game's shortest format, or can Somerset - the only team remaining without a nickname - reach the semi-finals for the first time since 2012?
You're in the right place to find out - but there is rain at Taunton, so how much, if any, cricket will we see?