Seasonal Changes in the Garden - September 2021

 In the northern hemisphere, September is the start of the meteorogical autumn. It is still warm enough to enjoy the outdoors and plenty to do in the garden. It is also a busy month bringing in the harvest before any chance of frost.

See here for links to the first 8 months of 2021. At the start of September (1st), there are roses, sunflowers, cosmos, hydrangea, geraniums, petunias, fuschias and more to enjoy and keep the bees interested. Butterflies are less common with just a few red admirals.

By the end of the month (30th), the colour palette is much reduced, nights are getting cooler and there is a nip in the air in the morning and evening. Apart from potatoes, parsnips and winter greens, which will stay in the ground through autumn and winter, the rest of the harvest has been gathered in. On the patio table, an overgrown courgette (marrow) and some of the Festival squashes are on their way to storage. 

Meteorological data for September 2021 are provided in the table below. September was a lovely warm month with daytime temperatures only dropping below 20 ℃ for 6 days at the beginning and end of the month. The Met Office also measured this month as having the highest CET temperature anomaly of 2021 (so far). Although rainfall was significant, 70% of it fell in the cooler last four days of the month. Last September (2020) was also a very pleasant month as I recall.

September 2021 (2020)

Weather Parameter



Average Monthly Temperature 

16 oC (15 oC)

Maximum Monthly Temperature

32 oC (29 oC)


Minimum Monthly Temperature

6 oC (3 oC)


Number of Air Frost Days

0 (0)

Number of Hot Days (> 25 oC)

5 (7)

5th - 8th, 24th

Monthly Precipitation

53.0 mm (17.4 mm)

Greatest 24 h Precipitation

17.8 mm (6.6 mm)

28th - 29th

Number of Dry Days

18 (20)

Monthly Sunshine Hours (estimated)

125 (135)

Average Wind Speed

2 km/h (2 km/h)

Highest Wind Speed

32 km/h (37 km/h)

26th, 27th

Maximum Barometric Pressure (Sea Level)

1033.8 hPa (1031.3 hPa)


Minimum Barometric Pressure (Sea Level)

998.7 hPa (992.4 hPa)


Average Barometric Pressure (Sea Level)

1018.0 hPa (1017.6 hPa)


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