You will see various ranges recommended but about 70°F to 80°F (21C to 27°C) is considered an optimum room temperature range for developing your sourdough starter.   In cooler room temperatures the starter will take longer to become active, and you will need more time between feedings. The starter will be more active at warmer room temperatures and you will need to feed it more often.   If anything, we hear more people complain of rooms that are too cool, rather than too warm. Try placing your starter on top of your water heater, refrigerator, or any other appliance that might generate some gentle heat. A turned-off oven, with the light turned on, can work well.    If you will be making a lot of sourdough and/or yeast risen baked goods, then consider investing in a temperature-controlled proofing box or heating element.   The temperatures at which your sourdough develops not only affects how quickly or slowly it becomes active, but it also affects how the yeasts and bacteria consume the sugars (present in the flour and other ingredients) and in which proportions. This also not only affects flavor – it also affects acidity, which in turn is associated with FODMAPs.