If there’s any doubt that summer is here, the near triple digit temperatures in Los Angeles the last few days remind us that the heat is on. The high temperatures also remind us that we need to stay hydrated, in particularly when working out.

Dehydration is serious, as it hampers our efforts at best and cause harmful injuries at worst. Our muscles, tendons, and ligaments all need proper hydration to perform at peak levels. Moreover, the majority of the brain is made up of water, so it stands to reason that a lack of hydration would negatively impact brain function. When dehydrated, the nervous system cannot efficiently facilitate communication between the brain and the body, causing a wide variety of symptoms, including fatigue, cramps, headaches and nausea. Obviously, all these conditions affect your workouts.

So be smart. Drink lots of liquid. Maintaining electrolyte levels is a good idea, too, to prevent cramping. As temperatures rise, the rate of dehydration increases. But dehydration rate is not the same for everyone, as everyone’s body is different. Sometimes the effects are subtle and you might not realize you’re dehydrated.

Here’s a pro tip on gauging whether you’re drinking enough water: It’s the bathroom test. If your urine is a dark yellow, you’re dehydrated. Drink some water now. Consult the chart below and enjoy your summer!