Did it feel like the 2nd warmest September on record for you in the UK? I must confess that feeling passed me by since it was still cooler than August and the rest of the weather was completely unremarkable.
The meteorological year starts in December which is why December appears as the 1st data point in the charts below. More information on the layout of the charts can be found in this post. Points lying between the upper and lower deciles are shown as open black circles, points lying between the lower/upper deciles and minimum/maximum are shown as solid black circles and any month with a new record is shown as solid black squares. All data is supplied by the Met Office and can be found here.
Every month I update 7 charts in all. I rotate which 6 appear in the deck above and 
plot the 7th as a separate chart here. In Spring & Summer, Frost (chart G) is shown here since that is of least interest in these months. At least it was until April 2021 when the record was smashed!
How abnormal was September 2021?
Chart H displays my UK Weather Abnormality Index (see my May 2019 post for details). The closer to zero this index is, the less abnormal and thus more “average” a month is. The higher it is, the more abnormal the month is. When the index is over 100%, we can describe the month as unusual in some way.
The abnormality index was 56% this month, bang in line with the median even though it was the 2nd warmest September on record.
PS: If you bookmark this link, it will be refreshed with the latest month’s data. I usually post the update in the first week of each month.
Click the relevant month to see my other weather trackers. Alternatively click the Weather Tracker hash tag below this post to see a list of all such posts.
- Click here for the latest month.
- 2021 – January, February, March, April, May, June, July, August, September, October, November, December
- 2020 – January, February, March, April, May, June, July, August, September, October, November, December
- 2019 – January, February, March, April, May, June, July, August, September, October, November, December
- 2018 – January, February, March, April, May, June, July, August, September, October, November, December
- 2017 – January, February, March, April, May, June, July, August, September, October, November, December
For analysis of trends by seasons, please click on the relevant season from this list or the Weather Trends hashtag below this post.
- 2021 – Winter, Spring, Summer, Autumn
- 2020 – Winter, Spring, Summer, Autumn
- 2019 – Winter, Spring, Summer, Autumn
- 2018 – Winter, Spring, Summer, Autumn
- 2017 – Winter, Spring, Summer, Autumn
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