As we all have likely experienced during the hot summer nights, sleep is more easily obtained in a cooler environment. This is due to the fact that the cooling of the core body temperature is an internal indicator to your brain that it is night time, and consequently sleep time. Keeping the bedroom cool can therefore help you fall asleep faster.
A room temperature of approximately 18.5 degrees Celsius (or about 65 degrees Fahrenheit) is suggested to be optimal for sleep. This allows your body to cool down without getting too cold.
Although this is less of a problem for the colder seasons, optimizing the use of a fan and/or air conditioning can help to keep the room cool. Keeping the blinds drawn shut may also help reduce accumulated heat during sunny days.
If you have a programmable thermostat, a trick is to schedule the temperature to slightly drop in the late evening before your usual bedtime. This will indirectly tell your body that it is time for sleep. Likewise, you can program the temperature to rise again in the early morning before you wake to make it easier to get out of bed.