Washington DC Weather in September

🇺🇸 United States

26°C

High

17°C

Low

Rain Days

Sunshine

65%

Humidity

North America › 🇺🇸 United States › Washington DC

Updated: March 2026

Is September a Good Time to Visit Washington DC?

6/10

Good

September is a good time to visit Washington DC (6/10). With 9 daily sunshine hours and only 10 rain days, this month delivers genuinely reliable outdoor conditions, ranking it 6th sunniest of the year in Washington DC. Culture-focused travellers and those who prefer lighter crowds will find September a practical choice, with prices running lower than peak June without sacrificing all the good weather. October offers a similar profile at lower hotel rates if dates are flexible. The main practical note: Washington DC's popular sites are busiest between 10am and 3pm regardless of season. Arriving at opening time or after 4pm makes a significant difference to the experience. Planning tips: accommodation is generally available without long lead times, and flight prices are typically lower than peak season. Flexible travellers will find the best deals by booking 2-4 weeks ahead. Mid-week arrivals consistently unlock lower hotel rates than weekend check-ins.

vs August:30°C avg high

Washington DC in September rewards travelers with average highs of 26°C and overnight lows around 17°C. Expect around 10 rainy days, so a compact umbrella is worth carrying. With 9 daily sunshine hours on average, conditions are warm and inviting for outdoor exploration.

26°C

Avg High

17°C

Avg Low

10 days

Rain Days

Sunshine

65%

Humidity

Temperature in Washington DC in September

The 9°C day-night temperature range is typical for continental climates: a light jacket in the morning that you shed by midday and need again after sunset. Humidity averages 65%, which is comfortable for most visitors. On warmer days, lighter fabrics help with the mild stickiness in the afternoon. UV index averages 6 this month, classed as moderate. Sunscreen is a sensible precaution for extended outdoor time, particularly at midday. Winds are calm at an average 14 km/h, so wind-chill is not a factor in planning your clothing. In Fahrenheit: 79°F average high, 63°F overnight low. Data sourced from Open-Meteo ERA5 climate reanalysis (1991–2020 normals).

Temperature in September

Monthly Precipitation (mm)

What to Wear in Washington DC in September

Morning17°CBefore the day warms up

Afternoon26°CPeak daytime temperature

Evening20°CAfter sunset cools down

Packing for Washington DC in September means dressing for 26°C days and 17°C evenings. A light cotton tee with a casual overshirt works well at 26°C, the overshirt doubles as a layer for air-conditioned venues. Evening temperatures settle at 17°C, a modest 9°C drop that a light cardigan or denim jacket covers. Comfortable walking trainers are the versatile choice for both outdoor sightseeing and indoor venues. A compact foldable umbrella weighs almost nothing and earns its keep across 10 potential rainy days.

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Local tip: Layers are more practical than a single heavy garment in Washington DC. The day-to-evening temperature shift rewards packing a versatile mid-layer you can add or remove as conditions change.

Events in Washington DC in September

September has no major festivals or public holidays in Washington DC, which is one of its practical advantages for independent travellers. Attractions run at lower capacity than during peak event periods, queues are shorter, and accommodation is easier to find without needing to book many months in advance. Local restaurants, markets, and transport operate at a relaxed pace, making this an ideal time for visitors who prefer a more authentic, unhurried experience of everyday city life rather than large crowds drawn in by a single major headline event.

What to Pack for Washington DC in September

Based on 26°C average highs and 10 rainy days

Light layers for morning and evening
Breathable T-shirts and comfortable trousers
UV-protective sunglasses
Quick-dry travel towel
Anti-chafe balm for long walking days
Moisture-wicking synthetic fabrics for active days
Compact folding umbrella
Waterproof outer layer or packable rain jacket
Quick-dry clothing that recovers fast after a shower
SPF 30+ sunscreen
Comfortable walking shoes (a second pair lets the first air out overnight)
Universal travel adapter
Small day pack for city exploration
Reusable water bottle

Best Activities in Washington DC in September

Explore outdoor markets and street food stallsMid-morning (10am-12pm)At 26°C, the temperature is ideal for extended walking without overheating
Guided walking tour of the historic centreMorning or late afternoonComfortable temperatures allow several hours on foot without fatigue
Visit rooftop viewpoints and observation decksGolden hour (1 hour before sunset)Warm clear evenings provide exceptional visibility for panoramic photography
Day trip to the surrounding countryside or coastFull day (depart by 8am)September is reliably dry enough for rural day trips without weather risk
Afternoon in a world-class museum or galleryAfternoon (2-5pm)Pairs well with outdoor morning activities and provides a mid-day rest from sightseeing
Coffee-house or traditional cafe culture experienceMid-morning or post-lunchA cultural ritual in this region that rewards slow appreciation regardless of weather
Evening live music, theatre, or opera performanceEvening shows typically at 7-9pmConsistent evening temperatures make getting to and from evening venues comfortable
Visit the main botanical garden or city park at seasonal peakYear-round; best light in morningSeptember brings distinct seasonal changes to public green spaces worth exploring
Seek out chilled local specialities: cold-brew tea, ice desserts, or chilled seafood at street-level stallsAny time; most atmospheric in evening marketsHot-weather street food culture peaks in September, with vendors setting up specifically for warm evenings

Why is Washington DC warm in September?

September brings the first meaningful shift toward cooler conditions in Washington DC, as the sun angle drops and day length shortens. Temperatures averaging 26°C by day and 17°C overnight are still comfortable by most standards, but the trend is clearly downward. At 39 degrees north latitude, autumn light has a particular quality: lower in the sky and warmer in tone, it gives the city a photogenic quality quite different from summer. Conditions remain excellent for outdoor activity, and crowds thin compared to the summer peak. Climate data: Open-Meteo ERA5 (1991–2020).

Sunshine Hours

The average number of hours per day with direct sunlight. Calculated from satellite measurements. Days with more than 7 hours of sunshine are ideal for outdoor activities. Under 3 hours means overcast conditions dominate.

UV Index

A scale from 0-11+ measuring ultraviolet radiation intensity. UV 0-2: Minimal risk. UV 3-5: Moderate -- wear sunscreen. UV 6-7: High -- hat and SPF 30+ essential. UV 8-10: Very High -- limit midday exposure. UV 11+: Extreme -- seek shade between 10am-4pm.

Rain Days

A rain day is counted when precipitation exceeds 0.1mm. This threshold captures even light drizzle. Unlike total rainfall in mm, rain days tells you how often you might need an umbrella, which is useful for planning outdoor activities.

Humidity

Relative humidity as a percentage. Below 40%: Dry -- skin and throat may feel parched. 40-60%: Comfortable -- ideal for most people. 60-80%: Sticky -- light, breathable fabrics recommended. Above 80%: Muggy -- heat feels more intense; quick-dry clothing is essential.

Frequently Asked Questions: Washington DC in September

In September, Washington DC experiences average highs of 26°C (79°F) and lows of 17°C (63°F). Expect around 10 rainy days and 9 hours of sunshine per day, with humidity averaging 65%. The 9°C gap between daytime and overnight temperatures is worth planning around: light layers work for most visitors during the day, but an overshirt or cardigan handles the cooler evenings. UV index averages 6, so sun protection is advisable on clear days.

Washington DC typically sees 10 rainy days in September, with total precipitation of around 116mm. Rain is moderate and manageable. Showers tend to pass quickly, and a light rain layer or foldable umbrella is sufficient protection for most days. For context, the driest month in Washington DC typically sees 4-6 fewer rain days than September.

Pack light layers, a light jacket for evenings, comfortable walking shoes, and sunscreen for Washington DC in September. Daytime temperatures of 26°C are pleasant, but the evening drop to 17°C means a jacket is essential if you plan to be out after dark. With 10 rainy days, bring a compact umbrella or waterproof jacket for unexpected showers. Comfortable walking shoes are a priority given the amount of ground most visitors cover.

Yes, September is an excellent time to visit Washington DC. With 9 daily sunshine hours and only 10 rainy days, conditions are ideal for sightseeing and outdoor activities. Temperatures averaging 26°C during the day are comfortable for long walks and outdoor dining. This is peak travel season, so booking accommodation in advance and arriving at popular attractions early in the morning helps avoid the busiest periods.

The average high temperature in Washington DC in September is 26°C (79°F), and the average low is 17°C (63°F). The mean daily temperature is approximately 22°C (71°F). The day-to-night range of 9°C is moderate, meaning a single light jacket covers most situations. These are 30-year climate normals based on the 1991 to 2020 reference period; individual years will vary, particularly in transitional months like spring and autumn.

The best month to visit Washington DC is generally August. August offers the most sunshine at 11 hours per day and only 11 rainy days. Average temperatures reach 30°C, making it comfortable for sightseeing, outdoor dining, and exploring the city. If your travel dates are flexible, planning your trip around August gives you the best chance of dry, bright weather.

September is shoulder or low season in Washington DC, meaning fewer tourists and generally lower prices than peak months. With 9 sunshine hours and 10 rainy days, the weather is less of a draw for mass tourism. This is an advantage for travellers who prefer a quieter, more relaxed experience with shorter queues and easier accommodation availability.

In September, Washington DC suits a range of activities thanks to mild temperatures around 26°C. Mix of indoor and outdoor activities works well given the moderate chance of rain. Top options include exploring historic neighbourhoods, visiting museums and galleries, local food markets, and day trips to surrounding areas. With 9 hours of sunshine, parks and waterfront walks are particularly enjoyable.

September ranks 6th sunniest of the year in Washington DC, with an average 9 daily sunshine hours. The driest months are October, November, and January. July is the hottest month (31°C avg high); January is the coolest (6°C). From here, temperatures fall 6°C into October. Compared to last month (August: 30°C high, 11 rain days), September is cooler and drier. September sits in the middle of the annual sunshine ranking for Washington DC, offering a reasonable balance of good weather and manageable crowds.

Year-Round Climate

Month	High	Low	Rain Days	Sun	Details
January	6°C	-2°C	9	6h	View
February	8°C	-1°C	9	7h	View
March	13°C	2°C	10	8h	View
April	19°C	8°C	10	9h	View
May	24°C	13°C	12	10h	View
June	29°C	18°C	12	11h	View
July	31°C	21°C	13	11h	View
August	30°C	20°C	11	11h	View
September	26°C	17°C	10	9h	View
October	20°C	11°C	8	8h	View
November	13°C	5°C	8	7h	View
December	8°C	0°C	9	6h	View

Other Months in Washington DC

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Plan Your Trip to Washington DC

Best Time to Visit Washington DC Washington DC vs New York in September

Data Sources for Washington DC

Washington DC on Wikipedia Open-Meteo Climate API NOAA National Centers UK Met Office WMO GeoNames

Climate normals represent 30-year averages (1991-2020). Individual years may vary.