As per traveler reviews, you're unlikely to encounter any as long as you don't wander off into the fields.
Snakes are everywhere in Greece except in Astypalea. But they are not a threat, as they are easily frightened off.
Most can be seen were roadkill having been squashed by vehicles while warming themselves on the roads. Snakes like south facing hillsides where they can bask in the sun, particularly if there is plenty of vegetation cover.
They will hear you coming long before you reach them and will be long gone. Sources suggest that if you need to walk across sunny hillsides, just wear a stout pair of walking boots.
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