It certainly brought good luck to Yorkshire, who beat Lancashire by five runs in a match reduced by rain to 18 overs per side.
In front of 15,396 spectators, who braved unseasonably chilly conditions, Yorkshire marked their biggest county game of the season with only their second win in eight T20 matches.
Sent into bat, they scored 141-7 before restricting the champions to 136 all-out in a tense finish.
The double rainbow appeared after a heavy shower 40 minutes before the scheduled 6.30pm start, which was put back until 7.25.
In contrastingly bright sunshine, Adam Lyth then gave Yorkshire the perfect start by rocking back to cut the first ball of the match from Nathan Buck to the backward-point boundary in front of the North East Stand.
In the next over, Lyth pulled successive deliveries from Jordan Clark over the East Stand rope as Yorkshire scored 29 from the first two overs.
Lyth holed out in the fourth over, miscuing a pull off Buck to Luke Procter at mid-on, and the runs dried up with his departure.
Alex Lees perished in the same over, caught by Liam Livingstone at cover, and Yorkshire did not manage a boundary after the fifth ball of the opening over until the fourth delivery of the seventh, Jack Leaning breaking the shackles by launching Steven Croft through mid-wicket.
Leaning cleared the mid-on rope when he deposited Stephen Parry towards the old pavilion, but he was yorked by a fine slower ball from Clark as the hosts fell to 76-3 in the 11th.
Kane Williamson added 44 with Leaning before his innings was also cut short, the New Zealander bowled by a quicker one from Parry.
Tim Bresnan was well caught at long-on by Clark off George Edwards, and Yorkshire slipped to 116-6 when Gary Ballance pulled Buck to Alviro Petersen at mid-wicket, Buck returning 3-25.
Clark judged another steepling catch at long-on to remove Andrew Hodd off Edwards, and Yorkshire were grateful for a handy cameo from Will Rhodes, who hit an unbeaten 24 from 14 deliveries.
Yorkshire’s total was no better than useful, but their spirits were lifted when Lyth took a brilliant catch at deep backward square-leg off Steve Patterson in the fourth over of the Lancashire reply.
Clark offered up one of the biggest skiers seen on this or any other ground, and Lyth made the chance look easy before presumably wiping snow off the ball.
In the next over, Leaning also took a fine catch in roughly the same position, Petersen whipping Rhodes firmly towards the North East Stand.
Lancashire fell to 49-3 in the eighth when Azeem Rafiq deceived Karl Brown with a well-flighted ball that bowled him as he tried to sweep.
The visitors were just behind at the halfway stage of their innings – 63-3 off nine overs compared to Yorkshire’s 68-2 – but Livingstone set about putting them ahead of the rate.
A powerful striker of the ball, he proved it by launching the left-arm spinner Karl Carver for a straight six into the Football Stand.
In Carver’s next over, the 11th of the innings, Livingstone lashed the first three balls – all full tosses – into the East Stand for six.
A single followed off the fourth delivery before Croft holed out to Leaning at deep mid-wicket off the fifth.
The batsmen crossed, and Livingstone was caught off the final ball when he again tried to find the East Stand, but succeeded only in picking out Ballance running in at deep-ish mid-wicket.
It left Lancashire 87-5 and tilted the balance, the visitors tumbling to 92-6 when Carver then took a catch at deep point when Arron Lilley sliced Rhodes.
Carver pocketed another catch – this time at deep square-leg – when Procter pulled Bresnan to deep square-leg, leaving the visitors 112-7.
To add to the drama, rain returned in the closing stages, potentially bringing the dreaded Duckworth-Lewis into play.
But with Yorkshire ahead on D/L, umpires Nick Cook and Jeff Evans kept the game going, and Lancashire slipped further behind when Tom Moores picked out Lyth at long-off off Patterson.
Lyth held another catch when Buck lashed Bresnan to long-on, and Patterson sealed it with two balls to spare when he had Parry caught behind.