 Big Z weather is a service of Alton Auto Butler. Revitalize your ride with the area's most trusted full-service car wash. At Express Detail, Alton Auto Butler, where every car gets the royal treatment. Mostly clear skies is the forecast. After an overnight low in the mid-60s, your Thursday should be a sunny day with a high in the mid-80s. Thursday night, mostly cloudy, a low around 70.