Seven games: five in Division One, two in Division Two
Division One leaders Surrey at home to Essex
Second-placed Hampshire play Gloucestershire at Cheltenham
Notts, leaders of Div Two, away to Derbyshire in East Midlands derby
Warwickshire v Kent 45-5
Image source, Rex FeaturesAfter steaming in for an hour, Ollie Hannon-Dalby can have a deserved rest.
His figures in the spell are outstanding - 7-4-15-5.
That is the 11th five-for in his career, with nine coming in the last five years and at 33, he is showing no signs of slowing up.
Somerset 55-1 v Yorkshire
Somerset opener Matt Renshaw is getting into his groove at Taunton and scoring quickly. He's up to 36 off just 41 balls.
The two Matts, Waite and Revis, are striving for another wicket for Yorkshire.
Warwickshire v Kent 43-5
It's the hottest day on record and a nightmare for bowlers, but Ollie Hannon-Dalby has five and it's not even midday!
Superb bowling and tactics here. Zak Crawley has been batting well outside his crease, so Michael Burgess moves up to the stumps.
And Hannon-Dalby obliges as he strikes Crawley on the pads and the finger goes up. It may have been missing off-stump, but the England opener has to go.
5-15 now for OHD and that's 40 Championship wickets this summer, and a third five-wicket haul achieved in just 34 balls.
Surrey v Essex 45-1
The Met Office has just said a new UK temperature record of 39.1 degrees celsius has been provisionally recorded in Charlwood, Surrey.
And it's not even midday yet. Quite extraordinary.
Meanwhile, just up the road at The Oval Alastair Cook is ticking along nicely for Essex. He's up to 20 with his side 46-1.
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Gloucestershire v Hampshire 40-0
All rather more sedate at Cheltenham, where Hampshire are ticking along nicely with Felix Organ and Ian Holland looking untroubled.
My worry is for Gloucestershire bowler Zak Chappell. With not a hair on his hand, I really hope he is using some extremely high-factor suncream.
Warwickshire v Kent 32-4
This is sensational!
Ollie Hannon-Dalby is ripping through the Kent top-order single handedly. He now has 4-12.
Jack Leaning is next to go, as he is hit in front and the finger goes up.
Northants 22-1 v Lancashire
What a start on his County Championship debut for Washington Sundar!
From just his second ball, Will Young goes back to cut but gets a fine nick into the hands of Lancashire captain Dane Vilas, who's got the gloves for this game.
A fairly tortured innings for the new Northants skipper, though, coming off 25 balls.
Surrey v Essex 35-1
Wise words at The Oval.
It's really not that pleasant out there. Temperatures are already above 37 degrees celsius in some spots. Crazy.
Image source, Rex FeaturesLeaders Nottinghamshire are off to a solid start with the bat at East Midlands rivals Derbyshire.
Haseeb Hameed (26 not out) and Ben Slater have taken them to 36-0.
Second-placed Middlesex have taken an early Sussex wicket at Lord's. Tim Murtagh dismissed Ali Orr lbw and Sussex are 21-1.
Warwickshire v Kent 28-3
Douse this man in cold water, Ollie Hannon-Dalby is on fire at Edgbaston!
He only needs three balls to get rid of Joe Denly and he is on a one-man mission to prove Will Rhodes' decision to bowl was a smart one.
Hannon-Dalby now has 3-12 from his four overs.
Credit to Chris Benjamin for this one, too, for a superb grab low down at gully.
Warwickshire v Kent 28-2
Oliver Hannon-Dalby is really bending his back this morning and he has his second.
Daniel Bell-Drummond is caught padding up with one that does not get up as much as he was expecting.
Somerset 25-1 v Yorkshire
Breakthrough for Yorkshire as Tom Lammonby snicks Jordan Thompson to first slip.
Somerset skipper Tom Abell comes in at three.
Image source, Getty ImagesSurrey v Essex 28-1
Alastair Cook is Essex's leading run-scorer this season, but quite some margin, with 658 runs heading into this match at The Oval.
I wonder if we'll see any beads of sweat on the former England captain's brow today?
He's 10 not out as the sun continues to beat down fiercely.
Gloucestershire v Hampshire 28-0
This match is taking place in the glorious surroundings of Cheltenham College and it marks the 150th anniversary of the Cheltenham Festival.
It is a busy one, too, with a fortnight full of cricket.
The schedule also includes the four-day match against Northants next week and the Royal London One-Day Cup game with Warwickshire being played.
While the Western Storm face the South East Stars in the Rachael Heyhoe Flint Trophy on Saturday and there is a 50-over game between Wiltshire and Glos on 31 July.
Back in 1872, Gloucestershire beat Surrey in the first game and no other cricket festival has gone on as long as this one.
Northants 13-0 v Lancashire
Image source, Getty ImagesA trio of early boundaries for Ricardo Vasconcelos at Wantage Road with opening partner and new captain, New Zealand batter, Will Young, yet to score.
Lancashire include new signing Washington Sundar in their XI. Sundar is a left-handed bat and off-spinner.
The Indian made his Test debut in Brisbane last January, taking Steve Smith as his first wicket and scoring 62 as India stormed the 'Gabbatoir', ending Australia's long unbeaten run there, stretching back to 1988.
Surrey v Essex 22-1
Kemar Roach overpitches and Nick Browne strokes it away through the covers for four.
Two balls later, though, the paceman produces one which just leaves him off the pitch and Ben Foakes moves to his left to take the catch behind the stumps.
Somerset 19-0 v Yorkshire
West Indies fast bowler Shannon Gabriel completes his second over at Taunton and there are just two runs from it, for Matt Renshaw.
Yorkshire will be hoping Gabriel has cured the no-ball problem that plagued him at Scarborough last week - and he hasn't overstepped yet.
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Jim: "Pitch and outfield looks really green at the Oval, unlike any other blade of grass I've seen in this country the last couple of weeks. A nice careful and watchful start might be useful and pile it on in the afternoon. #BBCCricket, external#SURvESS, external"
It must be great to have a job in county cricket - but on this particular day, maybe not the one in the photo.
Image source, Rex FSurrey v Essex 10-0
Wonder how many times Alastair Cook's first scoring shot in an innings was turned off his pads through square leg - must be a fair percentage, we reckon.
Sure enough a trademark boundary off Dan Worrall gets the former England skipper - who made 145 last week against Gloucestershire - up and running.