Weather data recording started in Penallt in March 2011. The charts below show the monthly summaries from January 2017 until the end of December 2017 and also compare Penallt’s 2017 weather with the 1981-2010 overall average data for Usk, the nearest place (16 km by crow) for which reliable data exist. Monthly maximum and minimum temperatures The chart shows that Penallt monthly averages mirrored the long term averages for Usk pretty well overall, with August and September showing the biggest difference, being around 2°C cooler than expected.
- June 19th and 21st were the warmest days of the year with a maximum of 30.8°C
- December 11th had the lowest maximum temperature of 0.5°C; there were no days with sub zero all day.
- Warmest by night was June 20th with a minimum of 17.3°C
- Coldest by night was January 22nd, with a minimum temperature of -3.8°C
- There were 58 days on which the temperature exceeded 20°C and 24 when it was below 0°C
- The mean annual temperature was 10.5°C, 0.2°C below the 2014 record warm year.
Overall, the total rainfall for 2017 was 972.6 mm (38.3 inches), 90% of the average Usk total of 1076.9 mm (42.4 inches) showing that the year was drier than normal overall – the driest since records began in 2012 too, the previous lowest being 1140.4 mm in 2016.
- Rain was recorded on 228 days in the year
- The wettest day was October 19th when 45.6 mm fell
- 20 mm or more fell on 7 different days