As Grace Road sweltered in the mid-30s, Yorkshire scored 255-2 after being sent into bat, the second-highest score in the 16 years of the 20-over tournament.
The only higher T20 score in this country was Yorkshire’s 260-4 against Northamptonshire at Headingley in 2017.
The world record is Afghanistan’s 278-3 against Ireland at Dehradun in February this year.
Yorkshire’s score proved far too good for a Leicestershire team who made 201-4 in reply, the visitors winning by 54 runs.
“It was a clinical performance right from the word go,” said first-team coach Andrew Gale.
“The batsmen performed their roles to perfection, and it was almost the perfect batting performance; we couldn’t have really done much better. It was an absolute belting pitch and a great game of cricket, with 450-plus runs for only six wickets.
“To win by 50-odd runs is a big margin in T20, and we’ll get a lot of confidence from this.”
Yorkshire’s innings was founded on three principal contributions.
Captain Tom Kohler-Cadmore top-scored with 96 not out from 54 balls with eight sixes and four fours, his highest T20 innings for the club.
Adam Lyth, with whom he shared a first wicket stand of 116 in 10.1 overs, struck 69 from 35 deliveries with four sixes and eight fours.
And West Indies overseas star Nicholas Pooran crashed 67 from 28 balls with six sixes and six fours, adding 121 for the second wicket with Kohler-Cadmore in 8.1 overs.
Yorkshire’s tally of 19 sixes – the other flying off the bat of Harry Brook – was only one short of the English record of 20 set only last Friday by Essex against Surrey at Chelmsford.
The match aggregate of 31 sixes equalled the English T20 record set in that same fixture between Essex and Surrey.
Yorkshire had looked on course to eclipse their own English record when their score stood at 236-1 after 18 overs, but left-arm medium-fast bowler Dieter Klein conceded only eight runs from the penultimate over and also picked up the wicket of Pooran with the second ball, the left-hander skying to deep backward-point.
Leicestershire’s bowling figures were as filthy as the heat and humidity for the 3,000 crowd, right-arm medium bowler Ben Mike the most expensive with 0-57 from four overs.
The most expensive over of the evening, however, belonged to left-arm spinner Callum Parkinson, who conceded 27 off his final over, the 16th of the innings, which included three sixes by Pooran, who struck the ball at times with such extreme brutality that he almost lifted himself off his feet in the process.
Under the weight of Yorkshire’s fearsome onslaught, which began from the moment that Lyth uppercut the second ball of the night off Klein for six over third man, Leicestershire’s fielding was village green at times.
At one stage, it was quite comical to see the portly figure of Australian batsman Mark Cosgrove consoling one of his team-mates over a wretched misfield, the sort that even Cosgrove, for all his bulk, would surely not have made.
Lyth and Kohler-Cadmore hit the ball all around the ground in their opening stand, Lyth reaching his half-century from just 21 balls as Yorkshire totalled 76 runs in the six-over powerplay.
Lyth’s second T20 career century looked likely to follow – he contributed 161 to the 260-4 English record two years ago – but the left-hander skied Parkinson out to deep backward square-leg.
Kohler-Cadmore reached his fifty from 32 balls and Pooran got to his from 22 deliveries, Pooran promoted up the order after the brilliant platform provided by the opening pair.
Leicestershire’s reply began pluckily enough under the circumstances, openers Cosgrove and Neil Dexter adding 51 inside six overs before Dexter was bowled by the expensive Duanne Olivier. But when Cosgrove and captain Colin Ackermann fell in quick succession, the cause soon became hopeless, a bit like trying to find cool areas in the ground on a summer’s night devoid of breeze.
Arron Lilley swatted 47 from 24 balls, picking out deep mid-wicket, and Lewis Hill finished unbeaten on 49 from 28, David Willey returning excellent figures of 0-23 from four overs.
Yorkshire pace bowler Matthew Fisher faces four-to-six weeks on the sidelines after dislocating his right shoulder during Saturday’s T20 match against Derbyshire at Chesterfield.
Fisher has also broke his left thumb and will see a specialist tomorrow regarding that injury.
Josh Poysden has joined the club’s walking wounded after being hit on the head in the nets. Poysden is being monitored by the club’s medical team and was replaced in the squad at Grace Road by Jack Shutt.