 Big Z weather is a service of Alton Auto Butler. Become a member today. Wash every day at one low price. Alton Auto Butler, where every vehicle gets the royal treatment. Sunny today, a high in the upper 80s. Northeast winds 5 to 10 miles per hour. Partly cloudy tonight with a low in the upper 60s. Mostly sunny Friday morning. Increasing clouds by afternoon and a slight chance of showers and thunderstorms. A high in the mid 80s. And Saturday, a partly sunny day with a chance of showers and thunderstorms. A high near 90 degrees.