Fifty shades of grey – a review of December 2021
December is often a cloudy month, but this time it excelled itself. We recorded sunshine on only eight days, to a grand total of just 16 hours and 30 minutes, or roughly 30 minutes per day (taking the Met Office definition of sunshine being a solar radiation reading of more than 120 W/m2 ) – and three and a half hours of that was on one day, the 2nd. We don’t have a long history of recorded sunshine data for Epping Weather stations, but according again to the Met Office, the typical figure for Essex in December is 52 hours.
It was also a mild month: our mean temperature was 6.8°C, the equal second warmest of our 37 years of records, and the warmest day on 30th at 14.3°C was also the second warmest on record (on a day when many places in the UK broke their warmest December day records). The temperature on 30th also never fell below 12.9°C, making it our record high minimum temperature. The overall lowest of the month was -0.4°C, our equal third highest minimum, and we recorded just two frosts in the month.
As for rainfall, it was another month of above average rainfall, with rain on 22 days totalling 73.2mm. The wettest day was Christmas Eve, with 18.6mm.
There were a few days when we recorded little or no measurable rain but there was mist or drizzle keeping everything wet – the average relative humidity for the month was 90.5%, and the lowest only at 73.0% on 8th, which coincided with our strongest winds of the month at Force 6, or 30mph, as we caught the fringes of Storm Barra.
In general, however, it was a fairly quiet month.
|Measure||Unit||Minimum||Average||Maximum||Average min||Average max||Total|
|Wind source (most common/highest gust)||Sector||N||WSW|
|Rain daily accumulation||mm||2.4||18.6||73.2|
|Solar irradiance during daylight||W/mý||47||294||127|
|Sunshine (sunny if irradiance >120 W/m2)||Hours||0.5||3.5||16.5|