The Mediterranean sea around Naxos is warmer all the year around than
the gulf stream's maximum temp around the C.I.s

Interestingly they seem not too disimilar for mean temps particularly in May
according to these sites

http://www.koufonisi.com/en/weather.shtml

and

http://www.jerseymet.gov.je/

Rainfall is noteably higher in Jersey during April/May which would be a
distinct advantage when growing spuds.

Sam