During the day, the sand at the beach is very warm; while at night, it is cooler. why does this occur?

this is because the sand has low specific heat which means that it takes a lot of energy to cause a change in temperature. plus it has a low capacity of weight per unit per degree temperature to absorb heatso yeah :)

 Because sand has a low specific heat, it has a low capacity per unit weight per degree temperature to absorb heat.This means that the temperature rises quickly in response (remember, temperature is the average kinetic energy of a system; not the heat capacity). It also is the reason why the sand cools quickly: the Temperature drops, as heat is released

Nimbostratus is the correct answer.
explanation: nimbostratus clouds are the type of clouds that are mostly likely present on gray, rainy day. these clouds produce continuous rain, snow and there is no thundering or lightening either.