Last year’s beaten finalists Hampshire made it four home group wins out of four as they thrashed Derbyshire by 143 runs at Southampton.
In only his second appearance in this year’s competition, Weatherley put on 113 for the second wicket with Nick Gubbins (62) as Hampshire piled up 295-8.
Derbyshire were already stumbling before their final four wickets went down for six runs in the space of nine balls, thanks to teenage paceman Dom Kelly becoming only the third Hampshire player to take a List A hat-trick – and their first since West Indies great Malcolm Marshall against Surrey in 1981.
After dismissing Zak Chappell and Harry Moore with the final two balls of the 35th over, the 18-year-old then returned to trap last man Daryn Dupavillon lbw to finish with 5-19 and bowl out the visitors for 152.
It was only a second defeat in the competition for Derbyshire, who return to action on Friday when they host Kent, while Hampshire and Worcestershire, who now go to co-leaders Somerset, are both on the road.
In a curtain raiser for next month’s T20 Blast quarter-final, also at Wantage Road, Somerset stole a psychological march on hosts Northamptonshire with a comfortable seven-wicket win.
In a match reduced to 49 overs a side by rain, Saif Zaib made 57 as Northants were bundled out for 155 in 37.3 overs, losing their last four wickets for just seven runs in four overs.
Opener Andy Umeed then led the way with 63 in 66 balls, blasting six fours and two sixes, as Somerset reached 156-3 in the 25th over.