A mostly sunny Labor Day in Chicago will close out with a round of thunderstorms and dangerous beach conditions that could linger for a day or more, forecasters say.

A small chance of showers at sunset Monday will build to 90% after 10 p.m., when thunderstorms are most likely, according to the National Weather Service.

Overnight rainfall totals are expected between a half and three-quarters of an inch.

A chance of rain will linger until the weekend.

Tuesday will most likely see more showers and storms, while Wednesday has a 30% chance of rain and Thursday, a 20% chance, the weather service said. Friday and the weekend have a “slight chance” of rain.

Meanwhile, waves along Lake Michigan will increase from a few feet Monday afternoon to 6 to 9 feet Monday night, the weather service said.

A beach hazard warning is in effect from 3 p.m Monday through Tuesday night. Strong rip currents are expected.

The weather service is also forecasting large temperature contrasts between the far south suburbs and areas father north. On Tuesday and Wednesday, temperatures north of Interstate 80 could reach the low 70s while areas south could reach the low 80s.