PHOENIX - An excessive heat warning begins Tuesday for the Valley and will remain in effect until Thursday as some of the hottest temperatures of 2019 so far are in the forecast.

The National Weather Service in Phoenix is issuing the warning for the Valley because temperatures could range between 106 and 113 degrees. 

Extreme heat is imminent 

That's exactly what the warning means, which is a little different for Phoenix.

Extreme heat warnings in Phoenix are based on a special computer model and not the same criteria that some of the other NWS offices use. If the city went by that criteria, there's a good chance Phoenix would be under an excessive heat warning all summer.

The computer model measures heat impact levels and the dangers they pose to people. The algorithm will factor in both the forecast high and low temperatures.

If that calculation produces a number that crosses over the "extreme" threshold - aka the 95th percentile - a warning is issued.

READ: Excessive heat warnings are a little different in Phoenix

Everyone needs to be prepared

Dangerous signs to watch out for if you're out in the heat too long are cramps, exhaustion, cool, wet, pale skin and headaches or dizziness. In the worst cases, these symptoms can lead to heat stroke.

READ: Phoenix is about to get very hot. What are the signs of heat stroke?

To stay safe, try to stay inside as much as possible, drink a lot of water and avoid alcohol, sugary drinks, and caffeine.

The Salvation Army sets up several heat relief stations across the Valley during excessive heat warning days.

LIST: Heat relief stations in place across Phoenix area as temps begin to soar

In addition to the blazing temperatures, there is also a high pollution advisory in effect Tuesday. The National Weather Service Phoenix says that means children and people with respiratory problems may have difficulty breathing.

To help keep the air cleaner, try to carpool and fill up gas tanks in the evening.