Division One leaders Surrey hit back after an early stumble against Nottinghamshire.
Jordan Clark smashed 107 as Surrey recovered from 70 for four to reach 339 for eight at the close of play on day one.
Clark helped dig them out of trouble with Sean Abbott (48), while Ben Foakes also hit 46.
Notts lost Jake Ball and Brett Hutton to injury, while Lyndon James claimed four for 74.
Kent struggled with the bat on the opening day against Warwickshire.
They were 95 for eight but Grant Stewart’s knock of 50 helped guide them to 171 all out. Only three others – Tawanda Muyeye, Jordan Cox and Matt Quinn – managed to make double figures for the hosts.
Oliver Hannon-Dalby took four for 56 and Henry Brookes claimed three for 55 in a dominant display with the ball for Warwickshire, who were 155 for two with Robert Yates 53 not out.
Their reply started strongly before Alex Davies was dismissed lbw by Joey Evison, with the score 69 for one.
Middlesex restricted Northamptonshire to 219 all out after a tight bowling display.
Saif Zaib top scored with 49 with no other batsman managed to score more than 31 for Northamptonshire. Ryan Higgins’ 33 for two was the pick of the bowling for Middlesex, who were 23 without loss at the start of their reply.
James Rew’s unbeaten 77 saved Somerset after they slipped to 80 for five against Hampshire.
The wicketkeeper and Kasey Aldridge (55 not out) put on an unbeaten stand of 116 for the sixth wicket before rain ended the day early with Somerset on 196 for five. Kyle Abbott’s four for 20 did the early damage for Hampshire.
A rain-delayed game at Lancashire saw Essex reach 12-1 with just under five overs in the day’s play.
In Division Two, Gloucestershire reached 280 for six on their opening day against Durham before rain cut it short.
Chris Dent plundered 85 and Miles Hammond struck 52 as Matt Parkinson claimed three for 45.
Tom Clark missed out on his first century of the season when he was caught for 96 in Sussex’s knock of 376 for seven against Derbyshire.
Tom Haines made 86 with Oli Carter hitting 56 at the close of play, with Alex Thomson claiming a three-wicket haul.
Adam Lyth’s unbeaten 75 and Finlay Bean’s 59 helped Yorkshire to 154 without loss during their rain-affected opener at Worcestershire.
Glamorgan and Leicestershire were not able to get going with rain ending any hopes of starting.
