Boise Weather in September
Boise in September averages 27°C (81°F) during the day and 10°C (50°F) at night. Minimal rainfall is typical for this time of year.
Rainfall in Boise in September
On average, there are about 5 days with rain during this month, averaging 13 mm (0.5 in). When rain does fall, showers tend to be light and brief. Most days will be dry.
Temperature in Boise in September
Boise in September has perfect weather. Days reach 27°C (81°F) and nights cool to 10°C (50°F). Conditions stay fairly consistent through the month, making it easier to plan what to wear. With lows around 10°C (50°F), nights are cold. The upside is that cool, crisp nights are often the best for a deep sleep.
Sunshine in Boise in September
Enjoy a sunny month with about 303 hours of sunshine, the clear skies make Boise even more beautiful.Our weather planner can help you find worldwide destinations with pleasant weather during this period. May, June, September and October typically offer the best weather for Boise.
Check the conditions for any month of the year.
For a detailed overview over the year and the best time to visit the United States of America, check out our Boise's climate page.
Boise Temperature in September
Min Temperature
10°C (50°F)
Max Temperature
27°C (81°F)
Chance of Rain
16%
Precipitation
13 mm (0.5 in)
Rainy days
5 days
Humidity
45%
Sunshine
303 hours
Percentage Sunshine
81%
Daily Historical Temperatures
50-year average (1976-2025)
Based on our historical records, temperatures in Boise typically drop from around 29°C (84°F) at the start of September to approximately 24°C (75°F) by the end. Nights are cool, with lows typically ranging from 9°C (48°F) to 14°C (57°F).
Average temperatures in September
Daily Historical Precipitation
50-year average (1976-2025)
Average daily rainfall for each day of the month based on long-term records.
Average precipitation in September
Historical weather for Boise in September
Browse day-by-day weather records for Boise spanning 51 years. Select any month and year to see actual temperatures, rainfall, and conditions recorded on each day.
Boise historical weather extremes in September
Based on 49 years of weather observations in Boise between 1976 and 2025, these are the recorded extremes.
- Boise recorded its highest September temperature of 40°C (104°F) on September 7, 2022.
- The coldest night in September in Boise was on September 24, 1984, with a minimum of -2°C (28°F).
Best Places in the United States of America in September
Find out more about the weather in the United States of America and which places have the best travel conditions in this month. See all of the United States of America in September →
perfect weather
pleasant
tolerable
unpleasant
poor
What to Wear in Boise in September
Warm weather calls for comfortable, breathable clothing in September. Cotton t-shirts, shorts, light dresses, and sandals are perfect. You might still want a light layer for evenings or air-conditioned places (for example buses). Almost no rain is expected, so no need to bring rain gear. And with plenty of sunshine hours, don’t forget sunglasses, sunscreen, and maybe a sun hat.What To Do in Boise in September
We rated the following activities from 1 (least suitable) to 10 (best) to do.
Check the conditions for any month of the year.
For a detailed overview over the year and the best time to visit the United States of America, check out our Boise's climate page.
Temperature Rainfall Sunshine Humidity
See the full Boise climate overview or explore weather in the United States of America.
