The only liquid elements at standard temperature and pressure are bromine (Br) and mercury (Hg). Although, elements caesium (Cs), rubidium (Rb), Francium (Fr) and Gallium (Ga) become liquid at or just above room temperature.
Clouds are a source of Infrared Radiation. When cloud coverage increases, the infrared radiation also increases. So the clouds basically act as space heaters. This emits energy towards the ground, which is what makes cloudy nights warmer. While with clear sky’s all the heat from the day just escapes back into the atmosphere so the temperatures will be colder.
Oceans, they are larger than ponds hence they possess wider exposure with more number of surface molecules.