Climate averages 1991–2020
Guidonia Montecelio weather
in September.
A warm, moderately wet month: the 4th warmest and the 8th driest of the year.
Long-term climate patterns, not a forecast for a particular trip.
September is a warm month in Guidonia Montecelio: daytime highs average 25.7°C and nights cool to about 15.3°C. By daytime temperature it is the 4th warmest of the 12 months.
Expect about 85 mm of rain on roughly 9 days, which makes September a moderately wet month (the 8th driest of the 12 months). Daylight, from sunrise to sunset, lasts about 12 h 32 min on an average September day.
The nearest other city in this atlas is Rome (21 km away). In September its highs average 25.3°C, about as warm as Guidonia Montecelio, with 84 mm of rain.
Among the 79 cities listed in Italy, Guidonia Montecelio ranks 14th of 79 for the warmest September highs and 40th of 79 for the driest September (rainfall, lowest first). The mean September high of those 79 cities is 24.3°C; Guidonia Montecelio is 1.4°C warmer than that mean.
From September to October, average highs fall by 4.8°C to 20.9°C, and monthly rainfall rises from 85 mm to 113 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
Guidonia Montecelio climate table
| Month | Average highHigh / low | Average low | Rainfall mm/month | Rain days ≥1 mm/day | Daylight hours/dayDaylight h/day |
|---|---|---|---|---|---|
| January | 11.1°C2.0°C | 2.0°C | 69 | 8.5 | 9.59 h |
| February | 12.1°C2.1°C | 2.1°C | 77 | 9.4 | 10.611 h |
| March | 15.2°C4.5°C | 4.5°C | 84 | 9.9 | 11.912 h |
| April | 18.4°C7.4°C | 7.4°C | 94 | 12.2 | 13.313 h |
| May | 22.9°C11.5°C | 11.5°C | 77 | 10.3 | 14.515 h |
| June | 27.7°C15.5°C | 15.5°C | 46 | 7.3 | 15.215 h |
| July | 31.1°C18.4°C | 18.4°C | 28 | 4.8 | 14.915 h |
| August | 31.5°C19.0°C | 19.0°C | 28 | 5.5 | 13.914 h |
| September, selected | 25.7°C15.3°C | 15.3°C | 85 | 9.4 | 12.513 h |
| October | 20.9°C11.6°C | 11.6°C | 113 | 10.4 | 11.111 h |
| November | 15.8°C7.4°C | 7.4°C | 132 | 12.4 | 9.910 h |
| December | 11.9°C3.3°C | 3.3°C | 104 | 10.3 | 9.29 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
- Rome in SeptemberItaly · 21 kmHigh 25.3°C · Low 16.6°C · 84 mm rain
- Acilia-Castel Fusano-Ostia Antica in SeptemberItaly · 41 kmHigh 24.4°C · Low 18.6°C · 86 mm rain
- Aprilia in SeptemberItaly · 45 kmHigh 24.4°C · Low 17.6°C · 91 mm rain
- Fiumicino in SeptemberItaly · 47 kmHigh 24.2°C · Low 18.9°C · 86 mm rain
- Latina in SeptemberItaly · 61 kmHigh 25.0°C · Low 17.6°C · 88 mm rain
- Terni in SeptemberItaly · 64 kmHigh 25.6°C · Low 15.0°C · 81 mm rain
- Perugia in SeptemberItaly · 127 kmHigh 22.6°C · Low 12.6°C · 79 mm rain
- Pescara in SeptemberItaly · 132 kmHigh 24.1°C · Low 16.6°C · 68 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 Guidonia Montecelio) is explained once on the Guidonia Montecelio year overview and on the Sources, method and limits page.