The 2 largest cities in Idaho are Boise with a population of  145,987 and Nampa with 81,557. The next 3 largest cities are  Meridian with 75,092, Idaho Falls with 56,813 and â¦ Pocatello with  54,255.
Averages for Washington DC in September. The weather in September in Washington DC is very attractive for those that want to avoid the peak heat of summer, yet still enjoy lots of warm days on their visit. On average, peak temperatures during the day in September still reach up to 27Â°C.
In the month of september, maximum temperature is 15Â°C and minimum temperature is 5Â°C (for an average temperature of 10Â°C). The climate is fairly cool around this city in the month of september, but it is liveable when dressing cosy. With 147mm over 16 days, you will experience some showers for your journey.