The mean annual temperature over the region varies from just over 9 °C to around 10.5 °C. Variations in temperature depend on both altitude, with a decrease of about 0.5 °C for each 100 metres increase in altitude, and proximity to the coast. Over the UK the mean annual temperature ranges from about 7 °C in Shetland to over 11 °C in the extreme south-west of England and the Channel Islands.
Temperature shows both seasonal and diurnal variations. January and February are the coldest months with mean daily minimum temperatures across the region close to 1 °C. They range from just above 0 °C on the Wolds to 1.5 °C or a little higher near the coast. This compares with below -2.0 °C in parts of the Scottish Highlands and over 5.5 °C in the Isles of Scilly.
Mean daily maximum temperatures range from just over 5 °C to 8 °C during the winter months and from 19 °C to 22.5 °C in the summer. These are comparable with values found in the summer in the London area which tends to be the warmest part of the UK. A noteworthy feature is that many of the UK maximum temperature records are held by stations in Eastern England. The highest known temperature recorded in the area was 37.3 °C at Cavendish on 10 August 2003 and 36.9 °C was recorded that day at Cambridge Botanic Garden and 36.5 °C there on 3 August 1990. The highest UK temperature stands at 38.5 °C at Faversham in Kent on 10 August 2003.
The variation of mean daily maximum and minimum temperatures month by month, together with the highest and lowest temperatures recorded, is shown for Cambridge Botanic Garden and Waddington, Lincolnshire.
Sea temperatures off the coast of eastern England vary from 5-6 °C in February and early March to 15-16 °C in August. The temperature is governed by the influx of warm water associated with the Gulf Stream. Temperatures tend to be lower in the south than the north in winter but heat up more rapidly and so the sea is warmer in the south during the summer months.
The number of days of frost is variable across the region although in East Anglia in particular, as the land is fairly flat, the main influence is proximity to the coast. An 'air frost' occurs when the temperature at 1.25 metres above the ground falls below 0 °C, whereas incidence of a 'ground frost' refers to a temperature below 0 °C measured on a grass surface. The average number of days a year with air frost ranges from about 30 at the coast to about 55 well inland.
The graphs show the average frequency of air and ground frost at Cambridge Botanic Garden and Waddington. Although frost is obviously more prevalent in the winter, there are occasional records of ground frost in July and August at inland locations. The warming effect of the sea can delay the start of the frost season at coastal sites.
