How much water should you drink every day to stay healthy and hydrated?

With a heat wave gripping much of the country, many people are guzzling more water than usual to try to stay cool and hydrated. The convention wisdom says we should be downing eight glasses of water a day. But that number isn't based on any scientific studies, and doctors say it's not necessarily the best advice.

A new article published in the Harvard Health Letter recommends drinking 30 to 50 ounces a day, an amount equal to about four to six glasses of water.

Drinking enough water is important to carry nutrients to your cells, flush bacteria from your system and prevent dehydration, especially during hot summer months when we lose more fluids through sweat. People who are getting a lot of exercise, or women who are pregnant or breastfeeding, may need more.

And while plain water is a healthy choice that won't add extra sugar and calories to your diet, other fluids can be part of the mix. "It's really about fluids in general. Doesn't necessarily have to be water," Dr. Sharmeela Saha, director of the dialysis center at University Hospitals Case Medical Center in Cleveland, told CBS News.

What you eat can make a difference too. Certain foods, including summer favorites like watermelon and other fruits, can count towards your daily water intake.

"Lettuce, spinach, fruits in general, soups ... those are all things that going to have a lot of water in them as well," Saha said.

Experts say don't ignore your thirst -- it's a sign your body needs more water. According to WebMD, other signs of dehydration may include weakness, dizziness, heart palpitations, sluggishness, fainting, or heart palpitations. Urine color may also indicate dehydration; if urine is dark yellow or amber colored, you're probably not drinking enough fluids.

In addition to keeping you well hydrated, some research has shown drinking water right before a meal may benefit your diet, taking the edge off hunger to help help you lose weight.