• In summer, the evenings are hot. The water is cool.
• There was no rainy season this time, but I remember that the water is generally cool during rainy season.
• During October-November, evenings are cool, but the water is waterwarm.
• In December, evenings are cold, but the water is freezing.
• In January, evenings are as cool as in November, but the water is still freezing.

I have thought of an explanation that uses day time temperature, convection, etc., but I am not sure whether it is physics or psychology that will give me the right answer.