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.
Looking at the weather in Washington, United States of America over the next 7 days, the maximum temperature will be 32â (or 89â) on Sunday 3rd September at around 2 pm. In the same week the minimum temperature will be 15â (or 59â) on Friday 1st September at around 11 pm.