Nine out of 10 suits boss Rennie down to the ground
Warriors were in a winter wonderland as they completed a brilliant Euro double over the French aces.
They shook off the shivers and jitters at sleety Scotstoun to snuff out Lyon for the second time in a week.
But this time they were made to work much harder for their Champions Cup success – Niko Matawalu emerging as the hero by grabbing both tries.
Now Dave Rennie’s troops will set their sights on the New Year – and the remaining group clashes with Cardiff and Saracens, knowing one more win could take them into the knockout rounds.
However, Rennie insisted his side’s failure to snap up a bonus point was no big deal.
Warriors had aimed to make it 10 out of 10 in the double header with the French outfit.
But the coach declared: “Nine out of 10 ain’t bad!”
Rennie added: “Before the matches, if anyone had offered me that against any top French team I would have jumped at it.
“We have given ourselves a great chance to go through to the knock out stages.”
Rennie admitted the win had come at a cost though, as George Turner faces a long layoff with ankle damage and suspected concussion.
With first-choice Fraser Brown already sidelined until February, Warriors face going into the festive Pro14 derbies against Edinburgh with only fringe men Grant Stewart and Kevin Bryce available.
Glasgow had made a dream start as they grabbed the lead after just 45 seconds.
Adam Hastings inflicted the initial damage by cruising into enemy territory.
Then Stuart Hogg’s chip was perfectly weighted for Matawalu to scoop up the ball and dive over.
The hosts retained control, forcing the French outfit to give away a spate of penalties.
And Hastings made amends for his conversion miss by slotting two in quick succession to open up a gap of 11 points midway through the half.
Matawalu then burst back into the contest to complete his touchdown double – with Hogg and Hastings again the creators.
The latter found the target from dead in front.
Lyon began to put phases together and only frantic home defending kept them out in the short term.
A powerful pack surge took them over the line in the 33rd minute, but video ref Geoff Warren ruled that the ball had not been grounded.
They maintained the momentum and Warren was back in the spotlight to rule out another effort for a knock on.
But he infuriated the Glasgow fans by endorsing a yellow card for Callum Gibbins for palming a rival player in the face – despite the fact he was clearly being illegally held at the time.
There was a further setback for Warriors when hooker George Turner was stretchered off and replaced by Grant Stewart.
And Lyon broke their duck with a penalty by Jean-Marc Doussain on the stroke of the interval.
The action was disjointed and scrappy after the restart – which was little wonder in the worsening conditions.
Lyon, now with the wind at their backs, were earning the bulk of possession.
And they delivered another blow to the Warriors as Pierre Louis Barrassi darted over in the corner – Doussain landing the tricky conversion.
Glasgow continued to make life difficult for themselves with basic errors being repeated and chances being squandered.
But they earned some breathing space as Hastings claimed his third penalty from close quarters.
There was drama 11 minutes from time when Lyon forward Etienne Oosthuizen was redcarded for a forearm hit on the face of Hastings.
And despite their numerical advantage, Warriors couldn’t add to their tally.