Short-Term Benefits
Cold showers boost recovery after exercise: Athletes often take ice baths after vigorous training do reduce soreness. You don’t have to take it that far, but you can obtain a similar benefit with a quick cold shower after your training sessions.
Cold showers increase mood and alertness: When cold water pours over your body, your breathing deepens in response to the shock of the cold (this is your body trying to keep you warm by increasing overall oxygen intake). Your heart rate will also increase, resulting in a rush of blood through your body that will help you get energized for the day.
Long-Term Benefits
Cold showers burn fat: There are two kinds of fat in your body: white fat and brown fat. White fat is the body fat we all know and struggle to get rid of. When we consume more calories than our body needs to function and we don’t burn those calories for energy, they are stored as white fat. Brown fat,"the good fat", is activated when we're exposed to extreme cold in order to generate energy and keep our body warm.Cold showers also speeds up your metabolic rate which helps to lose fat.
Relieve depressive symptoms: "A lifestyle that lacks certain physiological stressors that have been experienced by primates through millions of years of evolution, such as brief changes in body temperature(e.g cold swim) and this lack of "thermal exercise" may cause inadequate functioning of the brain.
Cold showers strengthen immunity and circulation: Remember how I mentioned that cold showers speed up your metabolic rate, which helps you lose fat? The increase of this rate activates your immune system, which releases virus-fighting white blood cells that will help you get sick less frequently. Cold showers also increase your overall blood circulation, which can help you avoid hypertension and the hardening of arteries.
But still there are various temperature degrees of cold water that may harm the body while some relieves it. For more information about these temperature degrees, visit:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4049052/
For more on the long and short term benefits, visit:
http://www.medicaldaily.com/benefits-cold-showers-7-reasons-why-taking-cool-showers-good-your-health-289524
http://www.lifehack.org/articles/lifestyle/surprising-benefits-cold-showers.html