3 Answers

Autumn, in October and November, still sees great temperatures but is often wet and overcast. Visiting the island in this season is recommended to those wanting to avoid the thick crowds of the peak season with an interest in exploring the island rather than in simply roasting on the beach. Sea temperatures are reasonable throughout the season and the air temperature remains around 20ºC during the day, slightly warmer at the beginning of the season, dipping just below at the end. However, night time temperatures drop to around 16ºC in October and 13ºC in November: extra layers are required. The sun diminishes drastically to around five hours per day, shared out between days of grey and those with blissfully clear skies. The beginning of the winter rains start to fall in October and increase throughout the season. While rainfall is limited to a few heavy storms, threatening clouds are a common sight. Another good reason to visit in this season is the landscape’s positive response to the much needed water.
Winter, from December till March, is mild but wet and blustery. Rainfall is at its highest in winter and falls on about half the days in each month. The wind can whip up real storms, though rain usually falls in steady showers, and forces the perceived air temperature plummeting down. Day time highs usually sit around 16ºC, falling below 10ºC at night but rarely below 5ºC. Subzero temperatures and snow are alien to coastal Crete though climate change has been known to bring this incorrigible pair to these shores; in February 2004 the temperature dropped to a record -0.8ºC and snow dusted the entire island. Conditions are generally preferable to those found at more northerly latitudes, for instance in England, and the odd clear day can receive temperatures near 20ºC, but summer-like weather should not be expected. The sea, around 15ºC, is okay for brave water sports enthusiasts with wetsuits but too cold for swimming.

https://www.peoplo.com/Crete+Weather

Wheather report in Crete in October can be found at the following links:
http://www.holiday-weather.com/crete/averages/october/
http://www.explorecrete.com/nature/crete-weather.html