Triple-digit heat, lower humidity kicks off first week of fall

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By Christina O'Haver By Christina O'Haver

PHOENIX -- The calendar says autumn begins Monday evening, but tell that to Mother Nature.

One-hundred-degree temperatures will make a comeback to the Valley of the Sun beginning Monday afternoon with a slight warming trend through Thursday.

A ridge of high pressure building into the region will produce a southwesterly flow of dry air. This will produce a pretty stable air mass that will keep storms out of most of Arizona and allow temperatures to rise.

While mornings will be rather pleasant, with the Phoenix-metro seeing low temperatures in the mid-70s and dew points in the 40s to 50s, Monday afternoon will see a high of 100. Tack on a degree or two each and every afternoon through Thursday. Skies should be mostly sunny.

By the end of the week, a Pacific storm system will push into our neck of the woods. This system will tap into some lingering moisture over Arizona and produce thunderstorms across much of the state Friday and into Saturday. This system will also drop Valley high temperatures back into the 90s.