Captain Josh Cobb with an over of his off spin to open us up at Wantage Road.

Nice tight start in this important rubber.

Image source, Rex Features

So no Reece Topley or Sam Curran this evening, but Surrey still have a formidable attack including Jamie Overton, skipper Chris Jordan, Jordan Clark and Dan Worrall.

Jordan opted to field first after winning the toss and he will be looking for one or two early wickets.

Stevie Eskinazi and Max Holden are the Middlesex openers - and remember, they have lost their last five T20 games.

Chris Peddy
BBC Sport at The Oval

The ground is starting to fill up after there were lots of empty seats a short time ago, and that's probably largely due to the fact that Oval tube station has closed for the night at short notice because of suspected flooding, so there'll be a lot of fans who have had to take a lengthy detour to south London.

As for the weather, there isn't a cloud in the sky on a lovely evening over The Oval. My phone is telling me it's still 30C and I'm not going to disagree, it's a very warm evening!

Hopefully the heat will drop to a more comfortable temperature for those with no cover over their seats as the sun begins to go down in the next couple of hours.

Somerset, second in the table, are looking to do the double on their West Country rivals Gloucestershire, fourth, in a match that could give them one foot in the quarter-finals or see the visitors leapfrog them in the table.

Hampshire, who begin the night just a point outside the top four, will have high hopes of keeping their campaign moving forward against bottom-of-the-table Kent at Southampton.

Third-placed Essex will feel likewise at home to Sussex, in sixth, where victory will see them stay right in the shake up for a top-two finish.

Behind Lancashire and Northants six teams are still in the mix for qualification.

Defending champions Notts have work to do with only three wins from seven and it's a big night for them at Edgbaston.

Yorkshire, in fourth, will hope to stay firmly in the hunt for a home quarter-final if they can win at Chester-le-Street.

Durham and Leicestershire are both three points outside the top four and both have home matches this evening - the Foxes against cut-adrift Worcestershire.

We will be focusing chiefly on Surrey v Middlesex and Northamptonshire Steelbacks v Lancashire Lightning in this text commentary page, and bringing you updates on the other games as and when we can.

As ever, ball by ball coverage is available on all tonight's games via BBC local radio and 5 Live Sports Extra. Select your match above to tune in.

Riverside: Durham v Yorkshire Vikings

Yorkshire won the toss and will bat

Leicester: Leicestershire Foxes v Worcestershire Rapids

Worcestershire won the toss and will bat

Northampton: Northamptonshire Steelbacks v Lancashire Lightning

Lancashire won the toss and will bat

Trent Bridge: Notts Outlaws v Birmingham Bears

Notts won the toss and put Bears in

Taunton: Somerset v Gloucestershire

Gloucestershire won the toss and put Somerset in

Kia Oval: Surrey v Middlesex

Surrey won the toss and put Middlesex in

Chelmsford: Essex Eagles v Sussex Sharks (19:00)

Toss to follow

Ageas Bowl: Hampshire Hawks v Kent Spitfires (19:00)

Toss to follow

Hoping for a bit of rain on your garden this evening? It looks like you are out of luck - see this helpful video from BBC Weather.

It's going to cool down a bit tomorrow, though.

Image source, Rex

Surrey have played 14 games in red and white-ball cricket so far this season and have yet to finish on the losing side.

In the T20 Blast, they lead South Group by three points after six wins and one no-result - but take on Middlesex in this evening's second cross-Thames derby without Jason Roy, Reece Topley and leading wicket-taker Sam Curran.

Roy made 81 off 45 balls when Surrey won by 20 runs at Lord's eight days ago but will his absence turn the tables in Middlesex's favour?

They certainly need to find some form after losing their last five in a row after beginning the Blast with three successive wins.

It was back in 2015 that Lancashire Lightning achieved their only trophy win in county cricket's shortest format.

But six wins from eight games in this year's T20 Blast suggests the North Group leaders are in the mood for another run to Finals Day.

They suffered their first defeat - against Durham - last week, but beat Northants by two wickets in a final-ball finish at Old Trafford earlier this month and are looking for a repeat.

The Steelbacks will again look to opener Chris Lynn, who has two hundreds and whose total of 379 runs is 81 more than any other batter, as second take on first at Wantage Road.

Image source, Rex Features

That was quite something in Amstelveen this afternoon, wasn't it?

We can't promise you three centuries in one innings and a world record total - although that would be nice - but we do have an exciting evening ahead in the T20 Blast.

Following a seven-day hiatus for a round of County Championship matches, the Blast is back with eight games, four in each group.

Welcome to our coverage. The first six matches begin at 18:30.

Image source, Rex Features

Durham v Yorkshire Vikings - BBC Radio Newcastle

Leicestershire Foxes v Worcestershire Rapids - BBC Radio Leicester & BBC Hereford & Worcester

Northamptonshire Steelbacks v Lancashire Lightning - BBC Radio Northamptonshire & BBC Radio Lancashire

Notts Outlaws v Birmingham Bears - BBC Radio Birmingham & BBC CWR/WM

Somerset v Gloucestershire - BBC Radio Somerset

Surrey v Middlesex - BBC Radio London

Essex Eagles v Sussex Sharks (19:00) - BBC Radio Essex & BBC Radio Sussex

Hampshire Hawks v Kent Spitfires (19:00) - BBC Radio Solent