The National Greek Weather Institute (EMY) has forecasted that the next couple of days rain will fall and phenomena like storm, hail and lightning can occur.
Be careful.
Below is the forecast of Skiathos (it was not possible to choose Skopelos)
http://emy.gr/emy/en/forecast/meteogramma_emy?perifereia=Thessaly&poli=Skiathos
skopelosnews 
Thanks for the update, from down under