The biggest drama of the night occurred in Southampton, as Hampshire, who had already tied with Somerset this season, did so again to end Surrey’s 100% start.
Surrey struggled to tame a slow pitch, with only Alice Davidson-Richards thriving with a 40, while fellow birthday girl Amanda-Jade Wellington picked up 3-25.
The visitors had looked to have locked up the match before Nancy Harman whacked 43 in 26 balls to turn the game into a last-over nail-biter.
The first five balls all saw singles – whether off the bat, leg or bye – and the last ball ended up as a run out as Rhianna Southby failed to get back for a second run.
Elsewhere, Warwickshire suffered a fourth successive defeat after being bowled out for 113 inside 19 overs.
Durham earlier totalled a battling 140-5 including a T20 career best 61 off 39 balls for Bess Heath.
Mady Villiers and fellow spinner Katie Levick then struck twice for polished Durham, as did the seam of Australian Heather Graham and Sophia Turner.
In Manchester, meanwhile, Somerset suffered their first Blast loss of the summer.
Having posted a modest 137-6 in their 20 overs, a total in which skipper Sophie Luff made 42, they were powerless to prevent Lancashire reaching their target.
Lanning and Eve Jones shared nine boundaries during a powerplay that yielded 62 runs as the hosts cruised to victory inside 16 overs.