Hales smashed an unbeaten 86 off 43 balls, with six of his eight sixes coming off successive balls, as his side chased down a target of 142 to beat Birmingham Bears by eight wickets.
Hales told Sky Sports: “I just gave myself a couple of overs to have a look at it but it was a beautiful pitch to bat on and the runs came easily.”
Opening partner Riki Wessels contributed 30 off 16 balls in a stand of 42 as Varun Chopra’s innings of 80 for the Bears proved in vain.
Elsewhere in the North Group, Durham beat Northamptonshire by 41 runs under the Duckworth-Lewis method.
Phil Mustard (51) and Calum McLeod (60) put on 84 in Durham’s total of 174 for eight and Northants were 47 for five from eight overs when rain ended the match.
Yorkshire eased to a seven-wicket win over Derbyshire at Headingley on the back of 17-year-old Matthew Fisher’s figures of five for 22.
That saw Derbyshire bowled out for 128 and Andrew Gale (41) and Jonny Bairstow (40no) saw Yorkshire home with more than three overs in hand.
Steven Croft hit a blistering unbeaten 70 as Lancashire chased a Duckworth-Lewis adjusted 140 to beat Leicestershire.
Kevin O’Brien’s 47 led the Foxes to 131 for seven in 15 overs and after a rain stoppage, Croft’s 39-ball onslaught saw Lancashire home off the last ball.
In the South Group, Glamorgan piled up 240 for three to beat Surrey by 25 runs at the Oval.
Colin Ingram top-scored with 91 from 47 balls, Jacques Rudolph hit 62 and Chris Cooke made 46 from 19 balls.
Dean Cosker then took four for 30 as Surrey came up short despite 58 from Steven Davies and an unbeaten 67 by Zafar Ansari.
Gloucestershire chased down Middlesex’s 175 for three with an over to spare to win by seven wickets, captain Ian Cockbain with 91 not out and Hamish Marshall 56 in their 179 for three. Nick Compton hit 78 for Middlesex.
Jimmy Adams hit 55 not out off 25 balls as Hampshire beat Essex by 17 runs.
In response to 173 for four, Essex were bowled out for 156 – Yasir Arafat taking three for 27 including top-scorer Ryan ten Doeschate for 68.
Kent beat Sussex by seven runs after making 185 for nine at Canterbury, Sam Billings with 46 and Sam Northeast 40.
Despite Chris Nash’s 61, Sussex were restricted to 178 for six.