2021 Weather Ups and Downs In Reading

By Roger Brugge

Averages and anomalies mentioned in this report refer to the climatological period 1991-2020. Historical records date back to 1901 for rainfall, 1956 for sunshine and to 1908 for most other weather elements.

2021 seemed to be a year in which the weather seemed to be always on the move in Reading, both up and down – a cool beginning, a warm spell in late March, a very cold and sunny April, slight snowfall in early May, a very wet June, a cool August, a mild September and October, and finally a very mild and rather dull December.

The end of winter 2020/21

Daily maximum/minimum air and grass minimum temperatures, January 2021.

The year started with a January that was wet, dull and cooler than normal. It was the coolest month of the year and the equal coolest January since 2017 – there were 14 air frosts but none of them severe. It was the wettest January since 2016 with over half the precipitation falling in the final week, leading to some flooding of fields and roads around the town. The total duration of 31.7 hours of sunshine made it the fourth dullest January on record, while there were 3 mornings with at least half the ground covered by snow at 9 a.m., but never deeper than 3 cm (on the 24th).

February was slightly milder than normal, but on the 8th the temperature failed to rise above freezing. The 11th saw the lowest temperature of the year. It was a February that gave wintry conditions before mid-month and spring-like conditions thereafter. The wettest day, the 4th, saw only 6.4 mm falling while there were three days on which fog persisted until after 9 a.m.

Spring

Daily maximum/minimum air and grass minimum temperatures, March 2021.

March was a dry month, with sunshine amounts and temperatures overall close to normal, although the final three days were quite warm. The 30th saw the temperature climbing to 22.5 °C, the second highest March temperature on record; this followed an overnight minimum temperature of 1.3 °C, giving an unusually large daily temperature range. Temperatures of 20 °C and above in March are rare. There was no sleet or snow during the month, but ground frosts were recorded on 20 mornings.

Daily maximum/minimum air and grass minimum temperatures, April 2021.

 April was more than 2.5 degC colder than normal, had the sharpest ground frost of the year (on the 17th) and was unusually dry – but had four days with snow/sleet falling. It was also the sunniest month of the year and the fifth sunniest April in our records. These conditions can be explained by high pressure and winds blowing from the east or north-east during the month. Snow lay 1 cm deep on the morning of the 12th – an unusually late spring occurrence of lying snow these days. Since 1908 there have only been five colder Aprils in Reading – the previous one being in 1986 – while the clear skies that led to cold nights (11 of which had an air frost and 25 a ground frost).

Daily sunshine and accumulation during April 2021.

Daily maximum/minimum air and grass minimum temperatures, May 2021.

Cold conditions continued in May, a month in which temperatures only rose above 20C during the final five days. The month was almost 2 degC colder than normal (helping to make it the coldest spring since 2013) and had an air frost on the 6th. There were 17 nights with a ground frost, while equally unusual was the fall of snow on the 5th. May was almost twice as wet as normal and, consequently, rather dull. May was as cold as May 2013, the wettest since 2007 and the dullest since 2006.

Summer

Daily rainfall and accumulation during June 2021.

June was 1 degC warmer than normal but was the second consecutive month to have a rainfall total that was almost twice the expected amount. The month was duller than normal – it was sunnier than the preceding May but still duller than April 2021. The first half of the month was warm and dry while in the second half temperatures barely rose above 20 °C. The second half was wet, largely due to the 17th with 29.9 mm being the wettest day of the year – and this was followed by a fall of 21.1 mm the next day. Another 21.6 mm fell on the 27th. In the second half of the month eight days each recorded no more than 1 hour of bright sunshine.

Daily maximum/minimum air and grass minimum temperatures, July 2021.

July was easily the warmest month of the year with the highest temperature of the year, 30.5 °C, recorded on the 20th. Rainfall was slightly less than average, and over 200 hours of bright sunshine were observed – but the month was still duller than April. After most of the month’s rain had fallen in the first 11 days, the 16th-23rd was a warm and sunny period.

Daily maximum/minimum air and grass minimum temperatures, August 2021.

August was a relatively cool month, being 1.7 degC cooler than July. The wet conditions of July continued for the first nine days of the month with little rainfall thereafter. The temperature only reached 23.9 °C – just marginally higher than the peak temperature of March and the coldest ‘hottest day’ in August since 1986. It was a dull month compared to normal – the dullest August since 2015 – and winds from the north-east were unusually prevalent. Persistent cloud led to cool days.

Autumn

Daily maximum/minimum air and grass minimum temperatures, September 2021.

Despite it being part of the meteorological autumn, summery conditions returned during September, which was the fourth mildest on record, but still about 1 degC cooler than in 1929, 1949 and 2006. Indeed, September was 0.1 degC milder than June and just 0.1 degC cooler than August. The highest temperature during the month of 28.7 °C was the highest in September since 2016 (29.2 °C) and 2006 (29.6 °C). Most of the rain fell during a final wet week, but the month overall was drier than average.

Daily rainfall and accumulation during October 2021.

October was warmer than average by about 1 degC with several very mild nights. It was the wettest month of the year (not surprisingly given our climatology), with wet spells around the 1st-4th, 15th-20th and 28th-31st. Over half the rain fell on just three days. But there were long, dry spells in between the days with rain and this helped to keep the sunshine total close to normal for the month. Winds from the south and south-west tended to dominate and there were no air frosts.

Daily rainfall and accumulation during November 2021.

November was the third driest on record with only 13.3 mm of precipitation, behind 4.7 mm in 1945 and 11.2 mm in 1901. It was also the driest month of 2021 in Reading, but one morning (the 29th) had slight lying snow after a heavy snowfall the previous night. November was colder than usual due to some cool nights and was also slightly sunnier than normal.

The start of winter 2021/22

Daily sunshine and accumulation during December 2021.

December was an unusually warm month, being 2 degC warmer than average overall and the warmest December since 2015. Nights were particularly mild and there were only 3 with an air frost. From the 24th onwards it turned unusually mild with 15.1 °C on the 29th making the day the equal sixth warmest in the records for December. The night of the 30th-31st was the equal fifth warmest December night on record with the temperature failing to drop below 11.9 °C. The 10th-23rd was almost without any rain, while the 11th to 30th was a remarkably dull spell with only 2.4 hours of sunshine in these 20 days. As a result, December was the dullest month of the year and the fourth dullest December on record.

Overall, the year was average temperature-wise, slightly drier than normal and the dullest since 2000. It was the coolest year (with 2016) since 2013 – reflecting the recent trend towards rising temperatures. Thunder was only heard on 6 days and none of these thunderstorms were noteworthy.

This blog was compiled using the daily weather observations made at the University of Reading climatological station – most of these being made by our chief observers Cahyo Leksmono and Ashley Dobie.

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