Climate averages 1991–2020

Suffolk weather
in September.

A warm, wet month: the 4th warmest and the 11th driest of the year.

Long-term climate patterns, not a forecast for a particular trip.

Average high 26.6°C Daytime mean, September

Average low 18.8°C Night-time mean, September

Rainfall 123 mm 11 days with ≥1 mm

Daylight 12 h Sunrise to sunset, per day

September is a warm month in Suffolk: daytime highs average 26.6°C and nights cool to about 18.8°C. By daytime temperature it is the 4th warmest of the 12 months.

Expect about 123 mm of rain on roughly 11 days, which makes September a wet month (the 11th driest of the 12 months). Daylight, from sunrise to sunset, lasts about 12 h 27 min on an average September day.

The nearest other city in this atlas is Portsmouth Heights (22 km away). In September its highs average 26.4°C, about as warm as Suffolk, with 120 mm of rain.

Among the 498 cities listed in the United States, Suffolk ranks joint 255th of 498 for the warmest September highs and joint 454th of 498 for the driest September (rainfall, lowest first). The mean September high of those 498 cities is 26.9°C; Suffolk is 0.3°C cooler than that mean.

From September to October, average highs fall by 5.2°C to 21.4°C, and monthly rainfall falls from 123 mm to 93 mm.

The annual picture

September in context

30-year average

Average highAverage low°C

Monthly rainfall

Average total · mm

Averages from hourly ERA5 reanalysis data. Actual weather varies from year to year. How these numbers are calculated

Every month, side by side

Suffolk climate table

1991–2020

Monthly climate averages for Suffolk, 1991–2020
Month	Average highHigh / low	Average low	Rainfall mm/month	Rain days ≥1 mm/day	Daylight hours/dayDaylight h/day
January	9.5°C1.1°C	1.1°C	88	9.3	10.010 h
February	11.3°C1.9°C	1.9°C	78	8.8	10.811 h
March	15.2°C5.1°C	5.1°C	100	10.6	11.912 h
April	20.6°C10.1°C	10.1°C	86	9.5	13.113 h
May	24.8°C15.0°C	15.0°C	97	10.8	14.114 h
June	28.8°C19.7°C	19.7°C	103	11.7	14.615 h
July	30.8°C22.2°C	22.2°C	128	14.8	14.414 h
August	29.7°C21.5°C	21.5°C	120	13.1	13.614 h
September, selected	26.6°C18.8°C	18.8°C	123	10.9	12.512 h
October	21.4°C12.9°C	12.9°C	93	7.6	11.311 h
November	15.7°C7.2°C	7.2°C	87	8.4	10.210 h
December	11.5°C3.3°C	3.3°C	89	9.5	9.710 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

Distance from Suffolk

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 limits

How these numbers are made (what the highs, lows and rain days mean, the sources and the model cell used for Suffolk) is explained once on the Suffolk year overview and on the Sources, method and limits page.