The rain held off for the deciding match at Grainville, and having won the toss Jersey opted to bat first.
It was a decision they looked like they would regret as they lost their opening three wickets for just two runs as Carlyon, Greenwood and Jenner were all sent back to the clubhouse.
Sumerauer played an innings-steadying knock of 34 off 21 balls but they were 58-4 when he was bowled by Stokes in the eighth over.
Jersey then lost four cheap wickets as they slumped to 74-8 off 11.4 overs as Guernsey seemed certain for a first-ever T20 series win over their rivals – and a first in any format for a decade.
But Will Perchard and Charles Perchard came together in an unbroken ninth-wicket stand of 56 – Will hitting 29 off 28 balls and Charles 26 off 23 as Jersey ended on 130-8.
In reply Guernsey’s batters also faltered as they slipped to 46-4 at the start of the ninth over.
Stokes – who went on to score a series-high 66 not out off 48 balls – and Ollie Nightingale (17) advanced the total on to 96-5 with four overs to go.
But Guernsey’s batters continued to struggle to support Stokes as Charles Perchard returned figures of 3-15 by dismissing Luke Bichard and Adam Martel in the final over.
Needing just seven runs, Perchard conceded just three off the over as Guernsey ended on 127-8, giving Jersey the most nerve-wracking of wins.
“I’m delighted to have got us over the line,” added Perchard.
“I fancy those pressure moments and I’m the captain, I take responsibility for the team.
“I’m delighted to have executed my skills and backed up by some amazing fielding in that last over as well.”
