Alastair Cook continued his outstanding early-season form on day one of a new round of Specsavers County Championship matches, which also saw an injury scare for James Anderson.
After Lancashire paceman Anderson limped off with groin trouble midway through his sixth over at Old Trafford, Yorkshire captain Gary Ballance (74) took over in the Roses match as the visitors recovered from a perilous nine for two to reach a hard-working 251 for six.
England's all-time leading wicket-taker, next scheduled back on duty for his country in the first Test against South Africa on July 6, did not return to the field in the Division One derby and will have his injury reassessed over the weekend.
Between the rain breaks down at Chelmsford, meanwhile, Cook (114no) chalked up his 58th first-class century on the back of his Royal London Cup exploits of late which have already earned him an automatic slot in next year's North-South series.
The former England captain marked his return to the championship in style as he and fellow centurion Tom Westley (111) piled on a second-wicket stand of 243 against Hampshire after Nick Browne departed without a run on the board.
Essex closed on that same total as Westley fell went to the final ball of the day.
Westley was just first to three figures, with his 15th four off his 178th delivery, and Cook duly followed an over later by hitting his 12th boundary off his 222nd ball.
Thunderstorms curtailed play to only 32.5 overs between Warwickshire and Somerset at Taunton, where the visitors closed on 93 for three and the Overton twins Jamie and Craig were responsible for all the wickets so far.
The top-flight action was completed, in the other derby of the round, by table-toppers Surrey and Middlesex at Lord's where, again between the downpours, Kumar Sangakkara (113no) had time to record his 59th first-class hundred.
The veteran Sri Lankan great hit 10 fours and for good measure two consecutive sixes off Ollie Rayner in his 132-ball century, also sharing a fourth-wicket stand of 114 with Dominic Sibley in a total of 265 for five before deteriorating conditions brought an early close.
In Division Two, midlands rain washed out day one between Leicestershire and high-flying Kent at Grace Road and allowed just 40 overs at Derby, where the hosts reached 111 for three against Worcestershire.
Leaders Nottinghamshire escaped the bad weather by heading west, and their trip to Glamorgan brought a fourth first-class hundred for opener Jake Libby (109) and 21st for Riki Wessels (120) out of 335 for six.
Libby's painstaking 213-ball century contained just nine boundaries as he and Wessels put on 123 for the fifth wicket - and then the latter raced to three figures with 15 fours from 119 deliveries.
For the hosts, Timm van der Gugten recorded admirable figures of 21-5-52-4.