Dr. Diana Lev with Dignity Northridge Hospital says when our bodies starts to lose water, it affects every single organ, including our brains. Most people feel the changes first in their sinuses.
"Sinus pressure is what starts off the headache, what increases the allergies and blocks your nose," said Lev.
The Accuweather sinus forecast for the Los Angeles area shows the next several days have a high chance of sinus pressure and discomfort.
And despite being in a heat wave, the risk of suffering a weather related migraine is moderate in the next few days and goes to low by next week. But with the dryness and the winds picking up, the forecast looks pretty grim for allergy sufferers.
"It's actually going to get significantly worse for anybody with allergies, sinus asthma, all those things," Lev said.
On top of the heat, the Accuweather health forecast for people with arthritis will experience some significant discomfort in the next few days. Lev says it's because joints are filled with fluid.
"If you increase pressure of blood inside any of those organs, including joints ... everything swells. So what happens when your joints swell? You have joint pain," she said.
And even if you don't have any health problems at all, Lev say you'll start to feel immediate changes once your body starts to lose water; it triggers an internal air conditioning mechanism, and you'll start to swell.
If you're going to be out in the heat, Lev recommends drinking eight ounces of water every 15 minutes.