"It's a dry heat." You've probably heard this before, or said it yourself. And many times, it is true. However, this morning (Friday), the humidity is palpable, and the high temperature is forecast above 110°F. Not so dry a heat...

An Extreme Heat Warning is still in effect through Monday.

Today, we'll be stuck with humid, hot air and not much to show for it (i.e. no thunderstorms). Instead, light winds and elevated ozone are expected. An Ozone High Pollution Advisory is in effect for today. PM10 (dust) should also remain locally driven.

Tomorrow (Saturday), however, will see signs of the monsoon starting to rev up again. In the afternoon, clouds and strong, gusty winds from thunderstorms to the east are looking more and more likely. Daytime ozone levels are forecast to decrease, but blowing dust could become an issue again. High PM10 levels will be possible, particularly for dust-prone areas.

Then by Sunday and early next week, uncertainty grows a bit more, typical of active monsoon periods. Light winds during the day will allow ozone levels to increase. But lingering cloud cover from a previous night's activity could delay ozone as well. Additional chances for dust will also be possible, perhaps Monday afternoon/evening.

We'll keep a close eye on ozone trends, and the monsoon outlook, to see if any changes to the forecast need to be made.

Check back on Monday morning for the next Phoenix Air Quality Forecast.

- M. Graves
ADEQ Meteorologist