 Big Z weather is a service of Alton Auto Butler. Where every car gets a royal treatment, all you have to do is pull in and let Alton Auto Butler do the rest. Partly cloudy tonight with a low of the upper 60s. Tomorrow, a mostly sunny start to the day. Increasing clouds by afternoon, a slight chance of showers and thunderstorms, and a high in the mid-80s. Friday night, cloudy with showers and thunderstorms likely. A low of the low 70s on Saturday, partly sunny. Chance of showers and thunderstorms, a high near 90 degrees. And sunny on Sunday, a high in the low 80s.