Missouri's Department of Health and Senior Services Section for Child Care Regulation requires:
A total of at least one (1) hour of outdoor play for children in attendance a full day unless prevented by weather or special medical reasons (Based on wind chill factor or heat index, children shall not be exposed to either extreme element.)Check with your licensing representative for details on what qualifies as "extreme" weather. As a general rule of thumb, if it's 40 degrees Fahrenheit or higher, your normal outdoor play routine should apply. Here is a windchill/heat index chart published by the Iowa Department of Health to help determine whether it's safe to go outside for a full hour, for shorter periods of time, or if you shouldn't take children outside at all.
Daily outdoor play, even in chilly weather, has many benefits for children. Gross motor activities, most easily done through outdoor play, are the best way to prevent obesity. Plenty of outdoor play can also have a big impact on the number of challenging behaviors experienced in child care programs. A simple change of environment can be a great way to refresh the children and the adults!
Be sure children are dressed appropriately for the weather. Dressing in layers is best, because layers can be taken off or added as needed. Be sure families in your program know that outdoor play is a part of your schedule, and children should be sent to child care with coats, hats, mittens, boots, and other appropriate winter wear. It's always a good idea to have a few spares on hand for children who left their coats at home.
For more information about safe outdoor play in the winter, check out this resource from the University of California.