Avg High
Calgary in September
Avg Low
Rain
Daylight
13h
What to expect
Calgary is in early autumn during September, a shoulder-season stretch where conditions can nudge warmer or cooler week to week. It generally feels mild and comfortable, and bigger day–night swings than you might expect. You get a comfortable daylight window for day trips and sightseeing. Conditions tend to feel steady, which makes planning simple.
September in context
How it compares to the rest of the year in Calgary.
Hottest (avg)
#4 / 12
Wettest (avg)
#5 / 12
Daylight Hours
#6 / 12
Windiest (avg)
#10 / 12
Highest UV
#6 / 12
Most Humid
#9 / 12
Monthly climate breakdown
Temperature
- Daytime high
-
- Nighttime low
-
- Feels like (avg)
-
Sunshine
- Daylight hours
- 12.6 h
- UV index (max)
- 6
- Typical sun hours
- 06:12 - 18:48
Rain & Snow
- Total rain
-
- Rainy days
- 10 days
- Cloud cover (avg)
- 50%
- Snowfall
-
Humidity & Wind
- Humidity (avg)
- 65%
- Wind (avg)
-
- Wind (max gusts)
-
Daily climate explorer
Day 15 selected for September. Typical high 20.4°C and low 6.4°C.
Typical disruptions in September
Based on 30 years of historical data, these are the disruption patterns most likely to affect plans in September.
Cold High impact
Cold feels-like nights Measures: Cold feels-like nights (min <=5C). Observed about 67% of days (20.2 days/month) in September. Historical risk signal only, not a day-by-day forecast.
20.2 days / month
~67% of days
Why this matters
- Expected days 20.2 days / month
- Probability ~67% of days
- Intensity Up to ~5°C (P95)
Cold feels-like nights are possible on ~20 days. Long outdoor blocks become harder to sustain, so layer up and keep a warm indoor fallback nearby.
Rain High impact
Washout risk Measures: Washout day risk. Observed about 8% of days (2.5 days/month) in September. Historical risk signal only, not a day-by-day forecast.
2.5 days / month
~8% of days
Why this matters
- Expected days 2.5 days / month
- Probability ~8% of days
- Intensity Up to ~23mm (P95)
Washout conditions are possible on ~2 days. Outdoor plans can become unreliable, so keep an indoor backup and flexibility around start times.
Rain Moderate
Rain disruption Measures: Likely rain disruption days. Observed about 8% of days (2.5 days/month) in September. Historical risk signal only, not a day-by-day forecast.
2.5 days / month
~8% of days
Why this matters
- Expected days 2.5 days / month
- Probability ~8% of days
- Intensity Up to ~22mm (P95)
Rain disruption risk appears on ~3 days. Outdoor plans can become unreliable, so keep an indoor backup and flexibility around start times.
Cold Moderate
Freezing nights Measures: Freezing nights (min <=0C). Observed about 6% of days (1.8 days/month) in September. Historical risk signal only, not a day-by-day forecast.
1.8 days / month
~6% of days
Why this matters
- Expected days 1.8 days / month
- Probability ~6% of days
- Intensity Up to ~-0°C (P95)
Freezing nights are possible on ~2 days. Fixed-time outdoor plans are safer with a backup option and flexible timing.
Snow Moderate
Snow days Measures: Snow days (>=0.1mm snowfall). Observed about 4% of days (1.1 days/month) in September. Historical risk signal only, not a day-by-day forecast.
1.1 days / month
~4% of days
Why this matters
- Expected days 1.1 days / month
- Probability ~4% of days
- Intensity Up to ~9.3mm (P95)
Snowfall is possible on ~1 days. Fixed-time outdoor plans are safer with a backup option and flexible timing.
Visibility Moderate
Fog-likely signal Measures: Fog-likely visibility proxy. Observed about 3% of days (1.0 days/month) in September. Historical risk signal only, not a day-by-day forecast.
1.0 days / month
~3% of days
Why this matters
- Expected days 1.0 days / month
- Probability ~3% of days
- Intensity Up to ~99% (P95)
Fog-likely conditions are possible on ~1 days. Fixed-time outdoor plans are safer with a backup option and flexible timing.
Show all disruptions (18 more)
Rain High impact
Washout run Measures: Multi-day washout runs. Observed about 0.5 days/month in September. Historical risk signal only, not a day-by-day forecast.
0.5 days / month
Probability unavailable
Why this matters
- Expected days 0.5 days / month
- Probability —
- Intensity Up to ~33mm (P95)
Multi-day washout runs are possible on ~0 days. Outdoor plans can become unreliable, so keep an indoor backup and flexibility around start times.
Wind High impact
Strong gusts Measures: Strong gust days (>=60 km/h). Observed about 1% of days (0.4 days/month) in September. Historical risk signal only, not a day-by-day forecast.
0.4 days / month
~1% of days
Why this matters
- Expected days 0.4 days / month
- Probability ~1% of days
- Intensity Up to ~77km/h (P95)
Strong gusts are possible on ~0 days. Exposed activities and transport links are more likely to be disrupted, so keep sheltered alternatives ready.
Rain Moderate
Heavy rain days Measures: Heavy rain days (>=10mm). Observed about 3% of days (0.9 days/month) in September. Historical risk signal only, not a day-by-day forecast.
0.9 days / month
~3% of days
Why this matters
- Expected days 0.9 days / month
- Probability ~3% of days
- Intensity Up to ~25mm (P95)
Heavy rain is possible on ~1 days. Outdoor plans can become unreliable, so keep an indoor backup and flexibility around start times.
Cloud Minor
Cloudy days Measures: Cloudy days (cloud cover >=60%). Observed about 41% of days (12.4 days/month) in September. Historical risk signal only, not a day-by-day forecast.
12.4 days / month
~41% of days
Why this matters
- Expected days 12.4 days / month
- Probability ~41% of days
- Intensity Up to ~100% (P95)
Cloudy skies are possible on ~12 days. Fixed-time outdoor plans are safer with a backup option and flexible timing.
Rain Minor
Wet days Measures: Wet days (>=0.1mm). Observed about 41% of days (12.3 days/month) in September. Historical risk signal only, not a day-by-day forecast.
12.3 days / month
~41% of days
Why this matters
- Expected days 12.3 days / month
- Probability ~41% of days
- Intensity Up to ~12mm (P95)
Measurable rain is possible on ~12 days. Fixed-time outdoor plans are safer with a backup option and flexible timing.
Cold Minor
Cold nights Measures: Cold nights (min <=5C). Observed about 39% of days (11.6 days/month) in September. Historical risk signal only, not a day-by-day forecast.
11.6 days / month
~39% of days
Why this matters
- Expected days 11.6 days / month
- Probability ~39% of days
- Intensity Up to ~5°C (P95)
Cold nights are possible on ~12 days. Long outdoor blocks become harder to sustain, so layer up and keep a warm indoor fallback nearby.
Rain Minor
Rainy hours Measures: Rain-hours signal (>=3h rain). Observed about 29% of days (8.7 days/month) in September. Historical risk signal only, not a day-by-day forecast.
8.7 days / month
~29% of days
Why this matters
- Expected days 8.7 days / month
- Probability ~29% of days
- Intensity Up to ~21h (P95)
Several rainy hours are possible on ~9 days. Outdoor plans can become unreliable, so keep an indoor backup and flexibility around start times.
Wind Minor
Gusty days Measures: Gusty days (>=40 km/h). Observed about 21% of days (6.3 days/month) in September. Historical risk signal only, not a day-by-day forecast.
6.3 days / month
~21% of days
Why this matters
- Expected days 6.3 days / month
- Probability ~21% of days
- Intensity Up to ~61km/h (P95)
Gusty conditions are possible on ~6 days. Exposed activities and transport links are more likely to be disrupted, so keep sheltered alternatives ready.
Cloud Minor
Mostly cloudy days Measures: Mostly cloudy days (cloud cover >=80%). Observed about 20% of days (5.9 days/month) in September. Historical risk signal only, not a day-by-day forecast.
5.9 days / month
~20% of days
Why this matters
- Expected days 5.9 days / month
- Probability ~20% of days
- Intensity Up to ~100% (P95)
Mostly cloudy skies are possible on ~6 days. Fixed-time outdoor plans are safer with a backup option and flexible timing.
Rain Minor
Wet most of day Measures: Wet-most-of-day signal (>=6h rain). Observed about 18% of days (5.4 days/month) in September. Historical risk signal only, not a day-by-day forecast.
5.4 days / month
~18% of days
Why this matters
- Expected days 5.4 days / month
- Probability ~18% of days
- Intensity Up to ~23h (P95)
Wet-most-of-day conditions are possible on ~5 days. Outdoor plans can become unreliable, so keep an indoor backup and flexibility around start times.
Humidity Minor
High humidity Measures: High humidity days (RH >=80%). Observed about 15% of days (4.5 days/month) in September. Historical risk signal only, not a day-by-day forecast.
4.5 days / month
~15% of days
Why this matters
- Expected days 4.5 days / month
- Probability ~15% of days
- Intensity Up to ~96% (P95)
High humidity is possible on ~4 days. Comfort and pace can drop quickly, so plan shorter outdoor blocks with air-conditioned backup stops.
Cold Minor
Cold days Measures: Cold days (max <=10C). Observed about 12% of days (3.5 days/month) in September. Historical risk signal only, not a day-by-day forecast.
3.5 days / month
~12% of days
Why this matters
- Expected days 3.5 days / month
- Probability ~12% of days
- Intensity Up to ~10°C (P95)
Cold daytime conditions are possible on ~4 days. Long outdoor blocks become harder to sustain, so layer up and keep a warm indoor fallback nearby.
Cloud Minor
Overcast days Measures: Overcast days (cloud cover >=95%). Observed about 8% of days (2.5 days/month) in September. Historical risk signal only, not a day-by-day forecast.
2.5 days / month
~8% of days
Why this matters
- Expected days 2.5 days / month
- Probability ~8% of days
- Intensity Up to ~100% (P95)
Overcast skies are possible on ~3 days. Fixed-time outdoor plans are safer with a backup option and flexible timing.
Other Minor
Low visibility proxy: same as fog-likely (RH ≥90% AND cloud ≥95%) — true visibility requires hourly visibility data Measures: Low visibility proxy: same as fog-likely (RH ≥90% AND cloud ≥95%) — true visibility requires hourly visibility data. Observed about 3% of days (1.0 days/month) in September. Historical risk signal only, not a day-by-day forecast.
1.0 days / month
~3% of days
Why this matters
- Expected days 1.0 days / month
- Probability ~3% of days
- Intensity Up to ~99 (P95)
Low visibility proxy: same as fog-likely (RH ≥90% AND cloud ≥95%) — true visibility requires hourly visibility data is possible on ~1 days. Fixed-time outdoor plans are safer with a backup option and flexible timing.
Cold Minor
Hard freeze nights Measures: Hard freeze nights (min <=-2C). Observed about 2% of days (0.6 days/month) in September. Historical risk signal only, not a day-by-day forecast.
0.6 days / month
~2% of days
Why this matters
- Expected days 0.6 days / month
- Probability ~2% of days
- Intensity Up to ~-2°C (P95)
Hard freeze conditions are possible on ~1 days. Long outdoor blocks become harder to sustain, so layer up and keep a warm indoor fallback nearby.
Cold Minor
Cold snap run Measures: Cold snap runs (>=3 cold days). Observed about 0.5 days/month in September. Historical risk signal only, not a day-by-day forecast.
0.5 days / month
Probability unavailable
Why this matters
- Expected days 0.5 days / month
- Probability —
- Intensity Up to ~9°C (P95)
Cold snap runs are possible on ~0 days. Long outdoor blocks become harder to sustain, so layer up and keep a warm indoor fallback nearby.
Heat Minor
Hot days Measures: Hot days (>=30C). Observed about 1% of days (0.4 days/month) in September. Historical risk signal only, not a day-by-day forecast.
0.4 days / month
~1% of days
Why this matters
- Expected days 0.4 days / month
- Probability ~1% of days
- Intensity Up to ~32°C (P95)
Hot days are possible on ~0 days. Midday activity often needs adjustment around shade, hydration, and indoor fallback options.
Other Minor
Heavy snowfall (INACTIVE until snowfall_sum units confirmed; set threshold once units are verified) Measures: Heavy snowfall (INACTIVE until snowfall_sum units confirmed; set threshold once units are verified). Observed about 1% of days (0.2 days/month) in September. Historical risk signal only, not a day-by-day forecast.
0.2 days / month
~1% of days
Why this matters
- Expected days 0.2 days / month
- Probability ~1% of days
- Intensity Up to ~11 (P95)
Heavy snowfall (INACTIVE until snowfall_sum units confirmed; set threshold once units are verified) is possible on ~0 days. Fixed-time outdoor plans are safer with a backup option and flexible timing.
Frequently asked questions
Is September a good time to visit Calgary?
Typical September days in Calgary reach highs of 18°C (64°F) with nights around 6°C (43°F). It usually feels mild by day and cold after dark. Overall, September sits in the middle of the Calgary climate range.
What are temperatures like in September?
Daytime temperatures in September typically peak near 18°C (64°F), while nights drop to around 6°C (43°F). Expect mild afternoons and cold evenings.
How much does it rain in September?
Rainfall in September averages 42 mm (1.7 in) across roughly 10 days. Overall it is a quite rainy time of year, so showers are usually brief rather than all-day downpours.
How many hours of daylight are there in September?
You can expect about 13 hours of daylight in September. Sunrise is typically around 06:12 and sunset near 18:48. Daylight is fairly typical, with enough time for sightseeing.
How strong is the sun in September?
UV levels are moderate (around 6); sunscreen and sunglasses are still a good idea.
Is it windy in September?
In September, average wind speeds are around 10 km/h (6 mph), with gusts on the windiest days reaching about 47 km/h (29 mph). On the ground, it is it often feels breezy, especially in more exposed spots or along the coast.