california just went through the hottest june on record, and july has continued to bring heat, with riverside and san bernardino reaching triple digits last week, and the mercury rising to an unthinkable 130 degrees fahrenheit in the valley of death. Since we may face more of these extreme heat events in the near future, we asked UC Riverside physicians Rajesh “Robby” Gulati and Brigham C. willis some questions you need to know, including how much (heat) is too much and how much (water) is not enough.
is there a temperature threshold at which heat becomes dangerous?
gulati: normal body temperature is 98.6 f. If the outside temperature is between 90 and 105 F, it can cause heat cramps. if between 105 and 130 f, heat exhaustion can occur. if it goes above 130 f, it can cause heat stroke.
When things get to this point, there may be loss of consciousness, skin may turn red, nausea, vomiting, dizziness, and other symptoms may occur.
what is the safe amount of time to spend outside of noon?
willis: The amount of time one can spend outside in the heat depends on many factors. body mass, heat acclimatization, age, etc., so it’s hard to say. Plus, if you stay well hydrated, it’s much safer to be outside in hot weather.
Temperature thresholds vary from person to person, but once it reaches 105°F or higher, the health consequences become more widespread. this varies with humidity levels; in very humid conditions it can be more difficult to disperse heat through sweat (that’s why a “dry heat” sometimes doesn’t feel as hot), how windy it is, and more. it also varies by age, with infants and the elderly being most at risk due to less efficient temperature regulation mechanisms. heat exhaustion and heat stroke become much more common above 110°F or so.
why is hydration important?
willis: Adequate hydration is essential for the proper functioning of all our organs. you need enough fluid and blood volume to maintain cardiac output, brain perfusion, kidney function, and more. the long-term consequences of severe dehydration can be just as bad as organ failure.
Usually in hot weather, you should drink at least 3 cups (24-30 oz; almost 1 liter) per hour to stay well hydrated. this amount should be maintained almost everywhere, though again with humidity level, activity level, and many other factors, this could vary.
what does dehydration do to the body and what are the long-term consequences, if any?
gulati: dehydration can cause muscle cramps, headache, dry mouth, thirst, fever, and low blood pressure. in severe cases it can cause loss of consciousness, lightheadedness, confusion, and palpitations.
The effects of long-term dehydration include continual muscle spasms and sometimes the eyes may become sunken. seizures may also occur due to electrolyte disturbances. the other effects can be urinary tract infections, kidney stones, and kidney failure. one of the more serious side effects can be a shock-like state of low blood pressure.
how much more water should you drink during 100+ degree weather?
gulati: one of the good parameters to control if you are well hydrated is through the color and quantity of your urine. the darker the urine, the more water you need. if you want to go into more detail, weigh yourself before and after exercise or before going out in hot weather for 2-3 hours and after. For every pound lost, replace it with 16 ounces of water.
As people travel this summer, should they be drinking different amounts of water depending on which part of the country they’re in?
gulati: drink when you are thirsty. that’s the body’s way of telling you it needs water. plain water is the best, you can also accompany the calorie-free and flavored waters. you can also add orange or lemon to the water. try to stay hydrated throughout the day instead of drinking a lot of water at one time. watch the color of your urine.
rajesh “robby” gulati, m.d. He is the Associate Dean for Graduate Medical Education and Designated Institutional Officer at the UC Riverside School of Medicine. Brigham C. willis, m.d., m.ed. He is the senior associate dean of medical education at UC Riverside School of Medicine.
