The prevailing wind is from the South West. This is an area of high rainfall (over 1,800 mm/year) with a 'micro-climate' determined by its position between mountains.

Current weather data is available for the upper Senni Valley, 1 mile south of Heol Senni, from a Davis 'Vantage Vue' weather station which is maintained by the Webmaster.

Graphs of the weather in Senni are also available for the previous week, the previous month, and the previous year.

The annual rainfall here is about 2,102 mm, making it one of the wettest parts of the U.K.

Global warming appears to be affecting the weather here, with extremes. These are likely to increase as atmospheric greenhouse gases are still increasing.

The wettest month was February 2020 with 559.4mm rain, over twice the average for the month. 2019 was the wettest year. On 20/09/2018, 3.75" rain fell in 12 hours. 250 mm (9.9") rain fell overnight 12 - 13/10/2018 during Storm Callum, the heaviest rainstorm many people here can recall.

The driest month was September 2014, with 14.4 mm of rain, only 10% of the average for September. April 2015 and 2917, October 2016 and May - July 2018 and April 2021 were also dry months.

The hottest day was 25 July 2019: 28.9°C at 14:49. (It was nearly as hot two days before that). On the same day, Cambridge had the hottest day ever recorded in the UK. A year earlier, on 26/07/2018, I recorded 27.3°C here.

Summary of monthly and annual rainfall up to 29/04/2021, (mm rain): (10 days of data for July 2016 are missing)

See also Weather forecasts & the current Senni river level at Pont Hen Hafod, half way between Heol Senni and Defynnog. Natural Resources Wales flood warnings, updated every 15 minutes.

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Updated 29 April 2021