Resuming the final morning on 48 for two after rain affected day three, the hosts raced to 333 for three before declaring to bring about an early lunch break.
Nash top-scored with an unbeaten 167 while Hamilton Brown was 126 not out when Sussex called a halt to their innings, allowing Yorkshire a reasonable crack at bringing about a result in two sessions.
At Derby, leaders Durham were all out for 325 for a first-innings lead of 27.
Derbyshire reached 22 for one at lunch but the match appears destined to end in a draw.
Somerset were set 133 for victory at Taunton after ending Surrey's second innings on 197 this morning.
Resuming on 97 for four, the visitors amassed just 100 more runs from their final six wickets, with Craig Meschede's four for 43 the pick of the Somerset attack.
Somerset reached lunch on 13 without loss, 120 runs away from victory.
The match between third-placed Middlesex and fourth-from-bottom Nottinghamshire at Lord's was delayed until 1.10pm due to rain. The match appears certain to end in a draw after the third day was called off without a ball being bowled.
In Division Two, Leicestershire reached 152 for five in reply to Lancashire's first-innings 453 for seven declared in a rain-affected clash at Old Trafford, while Worcestershire improved to 284 for six in reply to Hampshire's 428 in another rain-hit encounter.
Lancashire's title rivals Essex were again another side frustrated by the weather as they pushed for victory over Kent at Canterbury.
Kent began the day 56 runs in arrears on 113 for four after being forced to follow on, but no play was possible this morning as the poor weather continued.
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