Commercial HVAC in the South West

How different are Plymouth, Bristol and Cheltenham on the thermometer?

The South West is not one climate. On the Met Office's 1991 to 2020 averages the July daily high is 20.24°C at Plymouth, 21.74°C at Filton by Bristol, 21.82°C at Exeter Airport and 23.16°C at Cheltenham, close to the 23.89°C at Heathrow. Plymouth's 1,038 mm of rain a year is the wettest in the table; Heathrow gets 615 mm.

Met Office station	Average July daily high (°C)	Average January daily high (°C)	Days of air frost a year	Rainfall a year (mm)
Plymouth (Mountbatten)	20.24	9.01	13.44	1,038
Filton	21.74	8.08	32.93	819
Exeter Airport	21.82	9.08	not given	829
Hurn	22.24	8.74	55.98	877
Cheltenham	23.16	7.96	35.50	867
Lyneham	21.47	7.15	39.56	771
Heathrow, for comparison	23.89	8.42	26.99	615

Extremes now reach the region too. The Met Office lists 37.3°C at Yeovilton in Somerset on 25 June 2026 as the highest for its England SW district, and Cheltenham reached 35.9°C on 3 July 1976. In August 2026 the south-west England and south Wales average daily high was 23.5°C, 3.6°C above average, and the Met Office's county figures put the largest daytime anomalies, 4.3°C above normal, in Bristol, Gloucestershire and West Sussex. The same region also had the highest sunshine relative to normal, at 144% of average, which is what drives solar gain through glazing. Mild and wet is the rule for heating and ventilation; summer cooling is the exception that has to be designed for.

What does an office-heavy Bristol mean for plant?

In Bristol, Nomis puts professional, scientific and technical activities at 14.5% of employee jobs, information and communication at 7.4% and finance and insurance at 6.1%, against 8.6%, 3.9% and 2.8% for the South West. Office work is concentrated here, so comfort cooling and the equipment rooms inside offices are where cooling demand is likely to gather. The Bristol page goes to city level.

Bristol City Council launched its Keep Bristol Cool mapping tool after the second summer heatwave, in July 2022, and the city's One City climate work states an ambition to be carbon neutral and climate resilient by 2030. The council declared an Air Quality Management Area in 2001 whose boundary covers the central area and arterial routes, so intake position is part of ventilation design; see air quality management areas and ventilation. For heating, including boiler replacement, see commercial heating.

Is Gloucestershire the region's hot corner?

On the averages, it looks that way. Cheltenham's July high is the warmest of the six South West stations in the table. Nomis puts information and communication at 7.7% of Cheltenham's employee jobs against 3.9% for the South West, and Cheltenham Borough Council declared a climate emergency in July 2019 and committed to a net zero council and borough by 2030. In Gloucester, public administration is 8.7% of employee jobs and health and social work 21.7%, against 4.8% and 15.0% for the South West: buildings with long occupancy hours, where ventilation and temperature control are year-round duties. For cooling in those settings see commercial air conditioning.

What do the numbers say for Exeter and Bournemouth?

Exeter Airport's July high averages 21.82°C and its sunshine about 1,562 hours a year. Public administration is 9.2% of Exeter's employee jobs against 4.8% in the South West. Around Bournemouth, Hurn has a July high of 22.24°C and finance and insurance is 7.5% of employee jobs in Bournemouth, Christchurch and Poole against 2.8% for the region. BCP Council commits to making its operations carbon neutral by 2030 and aims for the area to be net zero by 2045, which it calls an ambition rather than a legal requirement.

What do Plymouth and Swindon add?

Plymouth leans towards industry: manufacturing is 12.7% of its employee jobs against 8.3% for the South West. The Plymouth and South Devon Freeport has two tax sites, Sherford and South Yard, designated from 4 July 2022. HMRC's manual describes a 100% first-year allowance for companies on plant and machinery for use in freeport tax sites, with a sunset date of 30 September 2031 for English freeports; it is not available to businesses chargeable to income tax. Heating and ventilation questions dominate there, so the Plymouth page and commercial heating are the natural reads.

Swindon is a logistics town in the numbers: transportation and storage is 11.6% of employee jobs against 4.4% for the South West. Big sheds raise heating and destratification questions before cooling ones; see warehouse heating and the Swindon page.

Who supplies the electricity?

National Grid Electricity Distribution says its network spans the width of the country from Penzance to Skegness. The Energy Networks Association's table lists it as the operator for South Western England and Scottish and Southern Electricity Networks for Southern England. NGED notes that increases to load may incur a charge under its published connection charging methodology for reinforcement works. The guide to electrical capacity for new HVAC plant shows how to check headroom before ordering plant; system costs are covered separately. A reader who wants a contractor's view can send an enquiry through the site's form.

Sources

• Met Office: Plymouth, Filton, Exeter Airport, Hurn, Cheltenham, Lyneham, Heathrow station averages for 1991 to 2020; UK climate extremes; top ten July temperatures; August 2026 regional breakdown; August 2026 county breakdown; checked 22 October 2026.
• Nomis (Office for National Statistics), labour market profiles for Bristol, Plymouth, Swindon, Cheltenham, Gloucester, Exeter, Bournemouth, Christchurch and Poole, the South West; checked 22 October 2026.
• Air quality legal requirements, Bristol City Council; Bristol One City climate page; Cheltenham Borough Council pathway to net zero; BCP Council climate and ecological emergency; checked 22 October 2026.
• Plymouth and South Devon freeport tax site regulations 2022, legislation.gov.uk; CA23122, HMRC internal manual; checked 22 October 2026.
• Distribution area and changing your electricity load, National Grid Electricity Distribution; find my network operator, Energy Networks Association; checked 22 October 2026.

Commercial HVAC questions in the South West

Does a Bristol office need cooling in a mild climate?

Often, yes. The July daily high at Filton averages 21.74°C, but offices carry their own heat from people and equipment, and August 2026 gave Bristol one of the largest daytime anomalies in the Met Office county figures. Bristol City Council also built its Keep Bristol Cool tool after the 2022 heatwave.

Can a Plymouth or South Devon business claim the freeport allowance on new plant?

HMRC's manual describes a 100% first-year allowance for companies on qualifying plant used primarily in a special tax site, with a sunset date of 30 September 2031 for English freeports. The Plymouth and South Devon Freeport's tax sites are Sherford and South Yard, so the plant must be for use there. The allowance is not available to businesses chargeable to income tax, and a tax adviser should confirm eligibility.

Does Bristol's Air Quality Management Area affect ventilation?

It can. The council declared the area in 2001 for nitrogen dioxide and particulate matter, and its boundary covers the central area and arterial routes. A building inside it may need its intake position and filtration checked.

Is Gloucestershire hotter than the rest of the South West?

On the Met Office averages Cheltenham's July high of 23.16°C is well above Plymouth's 20.24°C, and Gloucestershire had one of the largest daytime anomalies in August 2026. One hot summer is not a trend, though; the guide to whether the UK will need air conditioning sets out the projections.