Newly-crowned Division One champions Durham may not be able to end their season with a win after Sussex took control on a truncated day two at Hove.
The hosts finished the day with a lead of 162 after being bowled out for 328 in their first innings. Durham, who were 2-0 at stumps, had only managed 164 on the opening day.
Just 36.2 overs were possible because of bad light and after several inspections play was called off at 5pm.
Luke Wright (87 off 78 balls) missed out on a century but Ben Brown (64) and Ashar Zaidi (45) scored valuable runs to give their side a useful advantage.
Wright resumed on 74 and was dismissed when Chris Rushworth got one to nip back, keep low and crash into his stumps.
Zaidi, playing only his second first-class match in four years, continued where the England international had left off and was in sight of a half-century when he was caught at slip off Ben Stokes.
Brown, who had come to the crease with Sussex in trouble on 90-5, did pass the fifty mark before driving to point to give leg-spinner Scott Borthwick his second wicket just before lunch.
Chris Jordan (9) was well held at slip by Paul Collingwood when he propped forward to Borthwick before Graham Onions (3-103) had Steve Magoffin (13) caught at second slip.
There had already been one brief stoppage when thick mist rolled over the ground two balls into Durham's second innings.
The umpires made several inspections during the afternoon but with no breeze to shift the mist, the light did not improve sufficiently for there to be a restart.