Otter Valley Climate (2005 - 2017)

Weston Beach near Sidmouth.

Weston Beach near Sidmouth.

The Otter Valley is located in south east Devon and has formed over thousands of years of erosion from the River Otter which starts in the Blackdown Hills to the north and enters the sea at Budleigh Salterton. The Otter Valley is just one of quite a few valleys which run north-south, parallel to each other along this part of the south Devon coastline. There is the Clyst Valley to the west and the Sid Valley to the east with high ridges separating the valleys.

The climate here is described as maritime temperate and the native vegetation is predominantly broad-leaf forest consisting of ash, common oak (not sessile), beech and lime. Introduced species such as chestnut, horse chestnut, sycamore and holm oak also thrive here.

Table 1. Monthly averages and totals for the Otter Valley, Devon (2005 to 2017)

Temperature
(oC)

Humidity
(RH%)
Dewpoint
(oC)
Wind (mph) Rainfall
(mm)
Pressure
(hPa)
Air Frost* Thunder Soil Temp
(C)
Grass
Min
Sun Daily
Sun
Min Max Mean Min Max Min Max Max Mean Miles Gauge Mean Hours Days 30 cm 100 cm (C) Hours Hours
Jan 3.1 9.1 6.0 77 92 0.3 6.3 21.0 4.3 1950 90.2 1014.9 66.9 0.8 6.6 8.0 -1.8 80.0 2.6
Feb 3.0 9.3 6.0 73 92 0.4 5.7 20.6 4.4 1950 64.4 1014.5 58.7 0.3 6.4 7.5 -1.5 91.5 3.3
Mar 3.5 11.8 7.6 65 90 0.7 6.9 19.6 4.3 2186 66.8 1016.5 36.2 0.6 7.9 8.5 -0.6 140.8 4.5
Apr 4.9 15.1 10.0 56 88 1.6 8.3 17.9 3.9 2018 32.0 1015.5 6.8 1.0 11.2 10.6 1.3 188.6 6.3
May 8.1 17.9 13.1 60 91 5.1 11.3 18.6 4.1 2098 54.5 1015.0 0.0 1.5 14.0 13.1 4.4 203.4 6.6
Jun 10.8 21.0 15.9 60 92 8.3 14.0 16.6 3.5 1674 49.1 1016.1 0.0 1.8 16.7 15.2 7.8 219.8 7.3
Jul 12.7 22.5 17.6 61 93 10.0 15.4 16.9 3.5 1728 49.3 1014.8 0.0 2.4 17.8 16.6 9.3 221.0 7.1
Aug 12.2 21.5 16.9 64 94 9.9 15.4 16.7 3.4 1526 65.4 1015.2 0.0 1.5 17.4 17.0 9.1 193.1 6.2
Sep 10.8 19.7 15.3 66 94 8.4 14.4 15.9 3.0 1450 48.3 1016.7 0.0 1.0 16.1 16.3 6.3 169.8 5.7
Oct 9.0 16.0 12.4 73 94 6.5 12.4 18.1 3.5 1802 91.7 1014.9 1.7 1.5 13.6 14.5 4.1 127.1 4.1
Nov 5.2 12.0 8.6 78 94 3.2 9.4 19.4 3.9 1992 104.1 1013.0 29.1 0.9 10.5 12.1 1.1 95.8 3.2
Dec 3.2 9.3 6.0 81 93 1.0 7.2 20.1 4.3 2141 78.2 1016.4 81.4 0.2 7.0 9.1 -1.5 83.1 2.7
7.2 15.4 11.3 68 92 4.6 10.6 18.5 3.8 1877 793.9 1015.3 274 14 12.1 12.4 3.2 1803 4.9

Temperature:
The weather station is situated about 2 km from the coast on the relatively wide-open valley floor of the River Otter which is in south east Devon. The climate here is strongly influenced by the sea preventing extremes of temperature. During July 2006 whilst the Midlands and south east England baked in temperatures approaching 38C (~100F) the thermometer here reached a maximum of 30.8C. This was due to a sea breeze that regularly reaches here by mid-late morning. It seems that 30C is about the limit one could expect even on the hottest of days but despite this, the humidity remains high and the climate can be described as quite 'damp' which during hot weather can make it feel decidedly muggy and sticky.

In the winter time cold weather is again tempered by the sea and usually preventing any really severe frosts. Generally frosts are slight (-0.1C to -3.0C) and reasonably infrequent and only occur in calm conditions under clear skies when katabatic cooling leads to cold air settling on the valley floor. Some of the higher ground around here probably only gets a frost once or twice every winter.

Very occasionally cold air can arrive from the Continent due to a blocking situation preventing the normal warmth of the Atlantic from reaching here. It is under these circumstances that temperatures can plummet to very low levels if there is snow on the ground, such as in January & December 2010. Even so, ice-days are extremely rare (i.e., when the temperature remains below freezing all day) and temperatures are generally higher than those experienced further north and east in England. Though the majority of winters will be mild and with no snow such as the winters 2007, 2008, 2011, 2012, 2014, 2015 & 2016.


Figure 1. Temperature and rainfall for the Otter Valley (2005 - 2017)

Precipitation:
There is a definite drying out of the weather from March through to September with June & July being the driest and sunniest months. It can be so dry during the summer months that drought conditions prevail causing the grass to go brown all summer long. This is in direct contrast to the winters which can be so wet that everything remains sopping and rarely has the chance to dry out. Maximum rainfall occurs during October to January with a distinct drying trend in precipitation from late February onwards. Total rainfall for the whole year usually varies between 700 to 900 mm.

Snow:
A winter can pass and not one flake of snow will be seen falling, but more often snow will be seen falling on one or two occasions through the winter and early spring but it rarely settles here though December 2010 was exceptional as snow lay on the ground for 10 consecutive days. The hills on either side of the valley get a dusting once or twice during the winter time but even here, the snow will melt quite quickly and often will be gone within a day. No snow was reported falling or lying at this weather station in the winters of 2006/07, 2007/08, 2011/12, 2013/14, 2014/15 and 2015/16, no snow lay on the ground at any time in 2012/13 though was seen falling in March 2013.

Sunshine:
Being situated near the south coast the Otter Valley has a very sunny climate when compared to the national average. Yearly sunshine levels for the last few years have been around 1800 - 1900 hours with the year 2010 exceeding 2000 hours. This high level of sunshine occurs mainly on spring and summer days when the wind is from a southerly direction. It is under these conditions that the sun shines all day long through a clear blue sky yet just a few more miles inland cumulus cloud builds from mid-morning onwards turning unbroken sunshine into sunny spells. January has had the least sunshine since 2007 but you can still expect an average of 2-3 hours of bright sunshine daily with totals for the month ranging from 60 - 90 hours. Sunshine levels reach their peak from May to August with these months usually getting over 200 hours each. July 2013 had 328 hours of sunshine and so far, is the sunniest month yet recorded.


Figure 2. Sunshine and mean pressure for the Otter Valley (2005 - 2017).

Wind:
Being on a relatively wide-open valley floor the wind can be quite a feature, especially when blowing from a southerly direction. Winds from other directions have hills to deal with so we are quite sheltered to the west (Dartmoor), north (Blackdown Hills) and east (Fire Beacon). Sea breezes (from the south) dominate from late March to early September and that is reflected in the large bias towards the southerly direction in the radar map below. Land breezes are also common, especially from late September through to December and these gently blow from the north on cold, clear nights.


Figure 3. Wind direction for the Otter Valley (2005 - 2017)

 

Fog:
In view of the valley location and dampness of the climate you would have thought that fog would be more common but I have found that this is not the case and fog is quite rare here. Rather a different story to the nearby Exe Valley where fog is more common.

Figure 4. Soil & Sea Surface Temperatures for the Otter Valley (2005 - 2017)

Frosts:
Since this station was set up in 2005 there have been no air frosts recorded from May to September, and only 1 air frost has ever been recorded in October. Air frosts after mid-April and before November are very infrequent and usually only very slight.

Figure 5. Air frost duration and mean minimum grass temperatures for the Otter Valley (2005 - 2017)

Seasons:
Being near the south coast of Devon and on the South West peninsula of England, the climate here is one of the mildest in the British Isles and Northern Europe, and strongly influenced by the North Atlantic which moderates the temperatures more significantly than places further east and north.

Traditionally the timing of the seasons are said to follow the equinoxes and solstices, i.e., winter being the period between 21st December to March 21st. This may well apply in other parts of the world but here in the south west of England this timing of the seasons has little meaning. Meteorologically the seasons are better defined as Winter = Dec, Jan & Feb; Spring = Mar, Apr & May and so on. This divides the year up into nice, equal parts and is useful for weather recording but is a generalisation for the whole of the British Isles where the climate of northern Scotland is a world away from the climate here in the Otter Valley.

Here are my 'generalisations' for the seasons here in the Otter Valley and they roughly follow the cycles of natural world around us:

Winter (Dec - mid-February): Somebody once told me that down here in the South West you only get what he termed was a 'pseudo-winter'. I have a tendency to agree. Even though I call December a winter month the sea is still so warm that days with a maximum below 10C do not dominate until January (December 2010 was an exception!). Another person said that there is always a touch of spring in a Devon winter, and I think that is the best way to describe the months of December, January & February. The trees may be without leaves from mid-December onwards but you will still find a Herb Robert and primroses flowering in the woods and hedgerows in January and February where there is south-facing shelter.

Spring (mid-February - mid-May): Spring comes early to the Otter Valley and by mid-February nature seems be getting prepared. The dawn chorus is becoming very noticeable now, as is the lengthening of the day. Wild daffodils, 3-cornered Leeks and snowdrops will be in flower before the end of February and by early March the hawthorn and willow will be coming into leaf. By April the Devon Bank hedgerows are bursting into life with a mass of wildflowers and the fields turn yellow with buttercups and dandelions. At the end of April most of the trees will be in full leaf though the ash is always a late starter.

Summer (mid-May - mid-September): By mid-May the countryside has taken on its summer look with all the trees now in full, dark green leaf and will stay that way until well into the autumn.

Autumn (mid-September - November): Autumn feels like the shortest season, but due to the warmth of the sea it can stay surprisingly warm and October often produces summer-like days down on the beach. Air frosts are rare in October and usually do not appear until after mid-November.

Otter Valley Climate (1981 - 2010)

Otter Valley Climate 1981 to 2010 vs 2005 to 2012