SSEN's Weather Watch for September 2021

Colour weather image of the UK

The three months of Summer are now over and looking back at the period June to August 2021 we have some interesting statistics:

  • Northern Ireland experienced its third warmest summer on record and also observed its highest temperature on record with 31.3°C on 21 July at Castlederg in Tyrone.
  • Scotland has had its fourth hottest summer on record, and Clackmannan, Dunbartonshire, Perth and Kinross, Renfrewshire, Stirling and Falkirk, City of Glasgow and West Lothian had their hottest summer in records back to 1884.

Much of the UK had a dry and sunny summer, but there was a main exception. The Met Office maps in the image above show the south east of England, which recorded above average rainfall and below average sunshine levels.

We start September with a large area of high pressure centred near northern Scotland. This will slowly transfer east towards the Baltic Sea and as this happens, warmer air will reach the UK and Ireland. The hottest part of the month will be 5 to 10 September, during which time most places will be dry, sunny and very warm or hot with light breezes. The maximum temperatures are expected to be around 25 Celsius in most places but reaching 27 to 29 degrees in an area roughly from London across to Bristol.

The MetDesk map of Europe - in our summary page image - shows how the temperatures are forecast to differ from the long term average during the period 6 to 10 September. The red colours indicate well above average values, whereas the blue shading suggests much cooler than normal. During this time, Ireland, Northern Ireland, Wales and France will be particularly warm against expectations.

The weather is likely to turn cooler and changeable before the middle of the month arrives. Showers or outbreaks of rain will develop in most places, perhaps the heaviest occurring in south Wales and south England. The day time temperatures are expected to fall back to between 17 and 21 Celsius.

The for the last week of the month, we expect the weather to become mostly fine and dry again in many places.

Any tropical storms or hurricanes recurving north east across the Atlantic could impact the weather patterns and change the forecasts, so that’s one interesting scenario we’re keeping an eye on. Overall, September is expected to have a mixed month of weather, with a hot spell followed by cooler air with rain or showers.

We’ll be back in a few weeks to take a look at the projections for October and the remainder of the autumn.

About the author

Headshot of Simon Cardy

Simon Cardy Senior Meteorologist for SSE

Simon is the Senior Meteorologist at SSE and a Fellow Member of the Royal Meteorological Society. Through detailed analysis of the weather and climate, Simon provides valuable information to departments across SSE, including Networks (power distribution), Renewable Energy (wind farms and hydro dams) and Energy Demand Forecasting (how much electricity and gas we need each hour).

Read more articles by Simon Cardy