Why is water in lakes, rivers, swimming pool cold?

Answer 1

Evaporation drives the water cycle
Evaporation from the oceans is the primary mechanism supporting the surface-to-atmosphere portion of the water cycle. After all, the large surface area of the oceans (over 70 percent of the Earth's surface is covered by the oceans) provides the opportunity for large-scale evaporation to occur. On a global scale, the amount of water evaporating is about the same as the amount of water delivered to the Earth as precipitation. This does vary geographically, though. Evaporation is more prevalent over the oceans than precipitation, while over the land, precipitation routinely exceeds evaporation. Most of the water that evaporates from the oceans falls back into the oceans as precipitation. Only about 10 percent of the water evaporated from the oceans is transported over land and falls as precipitation. Once evaporated, a water molecule spends about 10 days in the air. The process of evaporation is so great that without precipitation runoff, and ground-water discharge from aquifers, oceans would become nearly empty.

Less evaporation takes place during periods of calm winds than during windy times. When the air is calm, evaporated water tends to stay close to the water body, as the picture above shows; when winds are present, the more moist air close to the water body is moved away and replaced by drier air which favors additional evaporation.
Which is why the water in lakes, rivers and swimming pool is cold.

Answer 2

It is because of evaporation. Each cubic centimeter that evaporates absorbs 60 calories from the lake. It is why when u go swimming in the desert u will freeze when u get out. It is because of the dry air which evaporates the water faster.

Answer 3

A lot of it comes from glacial run-off or cold underground springs. It takes a great deal of energy to heat a large volume of water even by a few degrees.

Answer 4

Evaporation does cool off water but it also takes very long to warm up because of high heat capacity. It cools off at night. It also cools your body much faster than air.

"Cold water robs the body's heat 32 times faster than cold air."
http://www.ussartf.org/cold_water_survival.htm

Answer 5

Because the ground around the water is a constant 55'F