In Chicago there are two seasons: Winter and Construction. But when it comes to your home's foundation problems, winter can be an ideal time of year to take care of cracks and leaks.
First of all, in the Chicago area the ground freezes around 40-inches below grade. That means that deeper than 3.5 feet, the ground isn't frozen and water is free to move about. When the ground freezes the soil expands. If you have a foundation problem, in cold weather heaving may occur. When this happens, the foundation wall moves or "heaves." This movement creates a space which then can fill with water coming up from below the frost line which will then freeze causing more movement, expanding cracks and creating a bigger problem come spring.
If you need to hear another benefit to getting your foundation repaired in the winter, again this has to do with the frozen earth. Exterior work is almost always cleaner when working with frozen ground. Digging machines don’t tear up grass as much when the soil is frozen. The removal of the top layers of soil and grass can be put back cleanly and neatly so come spring, the surrounding repair area will be back to normal quicker.
If you have a problem with your foundation, plan on calling sooner than later. And remember that winter can be an ideal time to get that leak fixed.