The frequency with which your furnace runs during cold weather depends on a few factors, such as the outdoor temperature, your thermostat settings, the size and insulation of your home, and the efficiency of your furnace. However, in general:

1. Typical Furnace Cycle: In cold weather, a furnace will typically cycle on and off every 15 to 30 minutes, depending on how much heat is needed to maintain the set temperature. The furnace may run longer during extreme cold spells.
2. Insulation and Home Size: If your home is well-insulated and has a smaller footprint, the furnace will cycle less frequently. Larger homes or those with poor insulation may require the furnace to run more often to maintain warmth.
3. Thermostat Settings: The higher you set your thermostat, the more often the furnace will run. If your thermostat is set to a temperature much higher than the outdoor temperature, the furnace will work harder to maintain that temperature.
4. Outdoor Temperature: In extreme cold (e.g., below freezing), your furnace may run more frequently because it has to compensate for the larger temperature difference between inside and outside. In milder cold weather, the furnace may cycle less often.
5. Furnace Efficiency and Age: Modern, high-efficiency furnaces will run for shorter periods but are more efficient, while older furnaces may need to run for longer cycles to keep up with heating demands.

If you notice that your furnace is running continuously without stopping, or if it isn't running enough to keep your home warm, it could indicate a problem, such as a malfunctioning thermostat, dirty filters, or issues with the furnace itself. Regular maintenance can help keep it running efficiently.