We can see fog all throughout the year. But we quite often see it after rain or snow if the conditions are just right. Any precipitation offers the moisture needed for the fog to form.
While there are many types of fog, there are two types we often see here in North Dakota. The first is radiation fog. This is probably one of the more common that we see. You need a lack of cloud cover and a lack of wind. As the temperature cools at night, the air cools to saturation and fog develops from the ground up.
Another type of fog we see here is advection fog. We see this when the ground is cool with rain or snow. A warm southerly and moist wind flows over the cool ground. This allows the air to cool to the dew point which allows fog to form.