Mold is something that is everywhere, it is ubiquitous, in the air we breathe. The main reason for mold growth, however is the combination of three aspects- food, moisture, and the right temperature. All of these things are found in the winter months or the wet months. Does this, however, mean that mold is exclusive to winter?
Winter is a time of year when the conditions for mold growth are more readily met in that there is a good amount of moisture in the air and the temperature is viable to sustain a few varieties of the fungus. It may seem like the freezing winter months will not be suitable, but most varieties of mold can survive and flourish even in sub zero climates. Crawl space mold is common in the winter months because of this. They create a small zone of highly humid air which will sometimes be of a slightly different temperature than the surrounding areas, allowing it to grow fast. If this is interrupted in any way, the mold can go into dormancy and becomes spores. Spores are a form of mold which can be reactivated by the heat-nutrient-moisture trinity.
The winter months provide ample opportunity for your home to have a basement leak either from burst pipes or rain. Melting ice and snow are also proponents of excessive basement moisture. Bear in mind that in some cases, mold cannot be completely avoided, but if caught early, it can be treated and its growth can be effectively halted.