Climate averages 1991–2020
Richardson weather
in September.
A hot, moderately wet month: the 4th warmest and the 4th driest of the year.
Long-term climate patterns, not a forecast for a particular trip.
September is a hot month in Richardson: daytime highs average 30.2°C and nights cool to about 21.1°C. By daytime temperature it is the 4th warmest of the 12 months.
Expect about 71 mm of rain on roughly 6 days, which makes September a moderately wet month (the 4th driest of the 12 months). Daylight, from sunrise to sunset, lasts about 12 h 24 min on an average September day.
The nearest other city in this atlas is Plano (8 km away). In September its highs average 30.1°C, about as warm as Richardson, with 71 mm of rain.
Among the 498 cities listed in the United States, Richardson ranks joint 113th of 498 for the warmest September highs and joint 219th of 498 for the driest September (rainfall, lowest first). The mean September high of those 498 cities is 26.9°C; Richardson is 3.3°C warmer than that mean.
From September to October, average highs fall by 5.5°C to 24.7°C, and monthly rainfall rises from 71 mm to 99 mm.
The annual picture
September in context
Monthly rainfall
Average total · mmAverages from hourly ERA5 reanalysis data. Actual weather varies from year to year. How these numbers are calculated
Every month, side by side
Richardson climate table
| Month | Average highHigh / low | Average low | Rainfall mm/month | Rain days ≥1 mm/day | Daylight hours/dayDaylight h/day |
|---|---|---|---|---|---|
| January | 12.7°C3.4°C | 3.4°C | 70 | 6.8 | 10.210 h |
| February | 15.1°C5.3°C | 5.3°C | 73 | 7.5 | 11.011 h |
| March | 19.1°C9.1°C | 9.1°C | 100 | 9.2 | 12.012 h |
| April | 23.5°C13.4°C | 13.4°C | 110 | 8.4 | 13.013 h |
| May | 27.4°C18.3°C | 18.3°C | 138 | 11.1 | 13.814 h |
| June | 31.4°C22.6°C | 22.6°C | 86 | 8.4 | 14.314 h |
| July | 34.0°C24.9°C | 24.9°C | 46 | 5.9 | 14.114 h |
| August | 34.0°C25.0°C | 25.0°C | 53 | 5.3 | 13.413 h |
| September, selected | 30.2°C21.1°C | 21.1°C | 71 | 6.2 | 12.412 h |
| October | 24.7°C15.2°C | 15.2°C | 99 | 7.8 | 11.411 h |
| November | 18.3°C9.2°C | 9.2°C | 93 | 7.0 | 10.510 h |
| December | 13.6°C4.6°C | 4.6°C | 91 | 7.1 | 10.010 h |
Rainfall is the average of the 30 separate monthly totals. A rain day is a local calendar day with at least 1 mm of precipitation. Daylight is the calculated sunrise-to-sunset length, not measured sunshine.
Compare places
September in nearby cities
- Plano in SeptemberUnited States · 8 kmHigh 30.1°C · Low 21.0°C · 71 mm rain
- Garland in SeptemberUnited States · 9 kmHigh 30.3°C · Low 21.1°C · 71 mm rain
- Carrollton in SeptemberUnited States · 15 kmHigh 30.4°C · Low 21.4°C · 72 mm rain
- Allen in SeptemberUnited States · 18 kmHigh 30.0°C · Low 21.0°C · 71 mm rain
- Dallas in SeptemberUnited States · 20 kmHigh 30.7°C · Low 21.5°C · 63 mm rain
- Mesquite in SeptemberUnited States · 24 kmHigh 30.6°C · Low 21.3°C · 64 mm rain
- Frisco in SeptemberUnited States · 24 kmHigh 29.9°C · Low 20.8°C · 81 mm rain
- Irving in SeptemberUnited States · 25 kmHigh 30.7°C · Low 21.5°C · 64 mm rain
Read the numbers correctly
Climate, not a promise.
These patterns help compare months. They cannot tell you the weather on a specific day of your trip.
Sources, method and limitsHow these numbers are made (what the highs, lows and rain days mean, the sources and the model cell used for Richardson) is explained once on the Richardson year overview and on the Sources, method and limits page.
Plano, Garland and Allen lie in the same rainfall cell, so their rainfall figures are identical to these; temperatures differ because they come from smaller 0.1° cells.