Re: Why is sand hot on some beaches but not others?

That's a good question!

I believe that I can offer several possibilities.

Firstly, the sand in Cancun is, I believe, composed of broken up shell 
material with some mix of sand, silt and clay.  The finely broken up 
shell material is called "coquina".  Coquina shell fragments are light-
colored, angular and often contain small holes called pores. This means 
that they 1) reflect sunlight more than a darker material would, thus 
absorbing less energy to turn into heat, and 2) have a greater surface 
area as compared to total mass than a round grain would have.  This means 
that they have a greater surface area to release heat through.  Finally, 
the coquina material tends to "wick" moisture up more than a round, solid 
grain would, and as the water evaporates the fragment cools down.

On the other hand, the sand in Connecticut or New York is more likely to 
be composed of rock fragments and rounded sand grains, as well as a 
greater percentage of silt and clay.  These sedments are more likely to 
be dark colored than the coquina and thus more likely to absorb sunlight 
to turn into heat.  The grains are also more likely to be less porous (ie 
with less holes in them) and more rounded.  This means in turn that when 
this material lies at the surface of the beach it is 1) less likely to 
absorb water and give off heat by evaporation, and 2) has a smaller 
surface area as compared to total mass than the coquina.  These 
characteristics mean that the Connecticut or New York sands will tend to 
be and stay, hotter.

I hope this helps. 

regards

JM Munsil, PG