Arizona truly has some extreme heat going on today. It's going to be so hot, the high temperature map will almost run out of colors.

I've tweaked color banks on weather graphics for almost 30 years. The trick is to get the colors to match the temperatures, as we have come to expect them. So cold temperatures are usually blue and purples, and hot temperatures are varying levels of red.

But sometimes extreme weather can make a graphic color bank hard to develop.

Look at the color bank weatherbell.com had to use for the extreme heat today in Arizona and California.

With high temperatures expected to hit 120 degrees in the Phoenix area, all of the hot colors are all used up. The color bank had to top out with green colors to depict temperatures over 120. Green used for extreme heat? What's left? What other colors could be used? All of the orange and red shades are used. The next stage of heat, depicted by what I would call violet colors, is blown right through on this temperature map. I guess finally you get so hot you turn green.

This truly is extreme heat. The National Weather Service in Phoenix forecasts a high of 117 degrees this afternoon at the official observing point. Here is what they are thinking for various cities in the Southwest.

High temperature forecasts from various cities in the Southwest. (National Weather Service - Phoenix, AZ)

It appears as though the all-time hottest temperature at Phoenix is 122 degrees back on June 26, 1990. The next few days are going to come close to all-time record heat in southern Arizona.

Is it really a dry heat?

Yes! At the time of the high temperature of 117 degrees, the relative humidity is expected to be 7 percent. You've never heard of a relative humidity of 7 percent in the Great Lakes. It's never happened. The lowest I've seen the relative humidity is 15 percent, and that was one time in the past 30 years.

In fact, it is going to be such a dry heat today in Arizona that the heat index formula computes to a feels-like temperature lower than the actual temperature. At the time of the 117 degree actual temperature, the heat index computes to 109.

You can call your friends and relatives in Arizona that rub it in on our weather in January. Ask them where they are today. The answer is inside.