Sunny skies in Chicago on Wednesday

CHICAGO (CBS) — Parts of Chicago have not recorded measurable rain in 18 days -- but that streak ends soon.

Unusually warm temperatures persist through the work week, with daytime highs in the 80s to near 90s. Average mid-September high temperatures are in the middle 70s.

As a storm system approaches from the West Coast, a first complex of showers and storms is possible in our area early Friday morning. Mainly, dry weather returns late Friday and Saturday, then there will be a higher chance of periods of thunderstorms Sunday into Monday.

Much of our area may record 0.5" to 1" of rain over the next seven days, which would be a welcome relief from developing drought conditions. Temperatures will finally cool next week into the 70s as the persistent heat ridge breaks down.

Tonight: Mostly clear. Mild. Low: 61

Tomorrow: Mostly sunny and hot. High: 90

Friday: Morning rain, then very warm and humid. High: 87