Coming from underground, generally spring water is warm, even hot. When water crosses the underground layers of rocks, dissolve them and come to the surface as mineral water, it's properties is different from region to region, even from spring to spring; the deeper the layer it comes from, the hotter the water. But the temperature is not necessarily the characteristic of these spring waters - the healing effect comes mostly, from the mineral composition of this springs and the Geothermal energy of this underground water, consider Hot Springs in Himachal Pradesh India (https://www.hotspringhealthcare.com/) for this very reason.

Thermal spring water facilitates healing in a number of important ways:

Bathing in hot springs gradually increases the temperature of the body, thus killing harmful germs and viruses.

Thermal bathing increases hydrostatic pressure on the body, thus increasing blood circulation and cell oxygenation. The increase in blood flow also helps dissolve and eliminate toxins from the body.

Hot springs bathing increases the flow of oxygen-rich blood throughout the body, bringing improved nourishment to vital organs and tissues.

Bathing in thermal water increases body metabolism, including stimulating the secretions of the intestinal tract and the liver, aiding digestion.

Repeated hot springs bathing (especially over three- to four-week period) can help normalize the functions of the endocrine glands as well as the functioning of the body's autonomic nervous system.

Trace amounts of minerals such as carbon dioxide, sulfur, calcium, magnesium, and lithium are absorbed by the body and provide healing effects to various body organs and system. These healing effects can include stimulation of the immune system, leading to enhanced immunity; physical and mental relaxation; the production of endorphins; and normalized gland function.

Mineral springs contain high amounts of negative ions, which can help promote feelings of physical and psychological well-being.

The direct application of mineralized thermal waters (especially those containing sulfur) can have a therapeutic effect on diseases of the skin, including psoriasis, dermatitis, and fungal infections. Some mineral waters are also used to help the healing of wounds and other skin injuries.

Lower Blood Pressure

A study at the Mayo Clinic found that soaking in a hot bath gives many of the health benefits of exercise with less strain on the heart! Soaking in a hot bath increases the heart rate while it lowers blood pressure rather than raising it as does other forms of exercise. Immersion in hot water first speeds up the heart to send blood to the surface and disperse extra body heat into the air. But after a few minutes, the warm blood causes the blood vessels to dilate, which lessens resistance to blood flow and lowers the blood pressure.

Sleep Better

Some medical experts recommend soaking in water of approximately 103 degrees Fahrenheit about two hours before bedtime (no longer than 15 minutes at a time) to help reduce insomnia. Studies suggest this can ease the transition into a deeper, more restful sleep. The temperature change may be a signal to the body that it's time to sleep, or the sensation of weightlessness may just be relaxing the muscles.

Improve Joint Mobility

The combination of warmth and buoyancy is extremely beneficial to arthritis sufferers. The buoyancy of the water relaxes the muscles, and supports and reduces stress on the joints which encourages freer movement. Relaxing the muscles helps to increase their range of motion. Many researchers now think rheumatoid arthritis patients can exercise safely if they follow tailor-made water exercises. Water therapeutically massages the joints with every movement. Water training can help increase aerobic capacity, muscle strength, and overall activity levels for RA patients.