Ninety degrees in the shade reckoned the Lord’s weather experts, who said that they had never known anything like it.
Throughout the day, spectators were told to keep well hydrated and were pointed in the direction of water fountains.
“Due to the extreme weather conditions, can we ask that spectators take extra care,’ said the PA announcer, with the brevity of a lifeguard warning of treacherous waves.
On the face of it, it was not a day for losing the toss and being consigned to several hours in the scorching outfield, which is exactly what happened to Yorkshire.
As London sweltered on the hottest day of the year so far, with just hazy wisps of cloud breaking up a deep blue sky, Middlesex made 337-4 as Sam Robson and Paul Stirling both hit hundreds.
Apart from at fleeting intervals, Yorkshire were not at their absolute best, but kudos to any bowler who can keep going in such conditions – particularly 39-year-old Ryan Sidebottom, who could have been forgiven for wishing that he had already retired in this, his final season.
So hot was it that one spectator in the Nursery End collapsed and had to be attended by St John’s Ambulance; it was noticeable how most of the 3,500 crowd gravitated towards the still sweltering shade.
After a minute’s silence for victims of recent terrorist attacks and tragedy, Sidebottom took the new ball from the Pavilion End from where he took three wickets in the opening over of the corresponding match in 2015.
This time, he began with a conventional maiden rather than one of the triple-wicket variety, although the opening delivery did go for four leg-byes off Robson’s pads.
Jack Brooks took the new-ball from the other end, his trademark headband not so much a fashion accessory as a necessity.
Sidebottom and Brooks kept things admirably tight in the opening exchanges, the cricket proceeding as slowly as spectators moving around in the enervating heat. Although it was a tough toss to lose, there was some green in the pitch and a smidgen of help for the bowlers at first.
But Yorkshire, who handed a Championship debut to 18-year-old batsman Harry Brook, who was preferred to Jack Leaning, were always up against it in a repeat of last year’s title decider.
Middlesex, without Adam Voges, Nick Gubbins, Dawid Malan and Tom Helm for various reasons, looked vulnerable on paper against opponents for whom leg-spinner Adil Rashid returned from England duty.
The visitors remained without Tim Bresnan, who sparkled in this fixture last summer and whose wife is expecting their third child.
Once Robson steered Brooks to the short offside boundary towards the Mound Stand, the first four off the bat in the eighth over, any early help for the bowlers had already vanished.
Robson and Nick Compton played well and with few alarms in the opening 90 minutes, defending solidly and seizing on errors in line and length.
But Steve Patterson got Yorkshire on the board when he lured Compton forward with a good one that licked the outside edge on its way to wicketkeeper Andrew Hodd.
In the next over, Robson was dropped on 31 by Brooks low down in his follow-through, not an easy opportunity, but one that he would want to have taken with conditions so much in the batsmen’s favour.
Another chance went down moments later, an even tougher one when a diving Alex Lees failed to cling on at third slip when Stevie Eskinazi edged Brooks.
It barely mattered, Brooks bowling Eskinazi for four with one that the batsman dragged on from just outside off stump.
At 75-2, Yorkshire had clawed their way back into it in the last half-hour before lunch, only for Robson and Paul Stirling to reassert Middlesex in a wicket-less afternoon. Fleet of foot and compact of style, Robson found gaps in the field with precision, while Stirling attacked at every opportunity.
Adam Lyth was swatted for six over long-on, and Stirling also hit nine fours in reaching a half-century from 69 balls.
Yorkshire bowled too many four-balls as Middlesex took tea on 228-2, although the visitors did tighten up once more in the final session.
Robson went to his hundred from the fifth ball after tea, late-cutting Rashid for three towards the Nursery End, and Stirling reached his century two overs later.
Rashid finally got Stirling lbw with one that kept low, ending a stand of 187 in 45 overs with Robson, who was dropped again on 144 in the final moments by a diving Rashid at cover off Brooks.
Sidebottom bowled James Franklin with the second new ball, but Middlesex won the melting day.