 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. Cloudy skies may give way to some clearing later this afternoon, definitely by tonight. With temperatures in the low to mid 80s for a high, west winds 5 to 10 miles per hour. Mostly clear skies tonight and a low in the mid 60s.