Dawid Malan moved from 145 to 153 not out during the only over possible on day two of his competitive home debut as Yorkshire and Derbyshire were frustrated by the weather at Emerald Headingley.
Rain and bad light is threatening to ruin this third round Bob Willis Trophy clash between the two teams with 100 percent records at the top of the North Group.
Derbyshire lead the way by four points in the bid for top spot, but Yorkshire have had the better of play so far in advancing to 288 for four from a total of 79 overs.
Left-arm quick Michael Cohen bowled the only over of the day, which was initially delayed until 3pm due to rain.
Malan pulled and cut him for two boundaries, the second of which brought up a sublime 150 off 185 balls, including 23 fours and a six.
Almost immediately, umpires Peter Hartley and James Middlebrook took the players off for bad light. Shortly afterwards it started raining, and play was called off for the day at 4.50pm.
Malan and Jonny Tattersall, who was stuck at the non-striker’s end on 64 not out, have shared an unbroken fifth-wicket partnership of 182.
It is likely that Yorkshire’s first priority at the start of day three will be to get the 112 runs they need in 31 overs to reach 400 and claim the maximum five batting bonus points.
Derby need five wickets in that time to secure three bowling points.
With only the two best placed group winners advancing to next month’s five-day final at Lord’s, bonus points could easily be a deciding factor come the end of the five-game group stage.