The storage condition has a big influence on the viability of the grass seed. During the winter season, places such as the garage can be cold or have high humidity levels. That’s why a garage is not ideal for storing grass seed. However, you can consider the garage if you have a good option for heating it. All you need is to ensure that the temperatures are below 90° and above 40°.  Besides, you can store the grass seed indoors. A fridge is a good option because you can adjust the temperatures settings. With this, you will extend the shelf life of your grass seed. Also: Universal grass catcher for side discharge in zero turn mower