Generally the liquid is water and the fluid above the liquid is air. The molecules within the liquid attract each other and at the interface there are more attractive forces towards the bulk of the liquid than there are towards the adjacent gas molecules. The molecular forces tend to pull into the fluid bulk.
Weather lowdown. Despite the fact that the month of September in Athens can produce summer-like temperatures, the weather starts to cool off significantly in October, and especially at night. The average temperature this month is 19Â°C (66Â°F), while the average low is 15Â°C (59Â°C), and the average high is 23Â°C (73Â°F).
The best time to visit Athens is in the fall and spring when the weather is agreeable and sunshine is pretty much a guarantee. Not to mention, crowds are thinner and hotel rates are cheaper. However, because of its Mediterranean location, Greece experiences warm weather throughout the year. Summer brings stifling heat and hordes of tourists, so we'd recommend avoiding Athens during this season.