The new month opens with warmer and modestly more humid air in Chicago and across the Midwest.

This warmth is the eastern extension of a huge warm air pool baking the West.

There, records are falling and the region finds itself in the grip of a full blow late-season heat wave likely to extend well into next week.

The issues with the warmth its sending our way aren’t nearly as far reaching.

But make no mistake, we’re in for some warm hours again Friday and will find warmth and “SW” winds dominant here into the first half of Saturday.

BUT CHANGE FOLLOWS WITH A SATURDAY AFTERNOON WINDSHIFT TO THE “NE”–A CHANGE LIKELY TO CHURN LAKE MICHIGAN, PRODUCING WAVES AND COOLER TEMPS

The weekend will start warm–a scattering of thunderstorms may bubble up in the unstable, moderately humid Saturday air mass.

But a “FULL FETCH”–in other words, FULL LENGTH OF LAKE MICHIGAN windshift to hit with a cold frontal passage Saturday afternoon.

As anyone who’s watched Chicago weather for any period of time, full fetch “NNE” winds create waves and rip currents.

The time such a flow spends over water offers it plenty of time to transfer wind energy to the lake surface and build waves.

On a holiday weekend, that may well cause some issues for mariners and swimmers.

Issuance of a BEACH HAZARDS STATEMENT seems a good bet on Illinois and Indiana shorelines and it wouldn’t be surprising to see waves building to 4 to 6 ft. on and adjacent to Chicago’s lakeshore Saturday afternoon and night—a situation likely to spill over into Sunday.

“NE” winds will continue Monday (Labor Day)–but the pressure gradient is to “relax” which one would hope will bring wind velocities down—-and along with them, ease wave heights as well.