Photo: Sionk · CC BY-SA 4.0Few UK towns have warmer summer afternoons than Harwell
January nights here settle around 1.7°C (35°F). Only 21°C separates winter nights from summer afternoons. Its yearly rainfall falls short of 89% of UK towns. Gritters and ice scrapers earn their keep on roughly 46 nights a year below 0°C.
Met Office 1991–2020 averages for the town itself.
A year in Harwell at a glance
Each month’s typical high and low, in °C.
What a year in Harwell feels like
Typical highs and lows by season and by month, from the Met Office’s 1991–2020 averages.
About 618 mm of rain a year
November is the wettest month and March the driest. About 14 days a year bring 10 mm (0.4 in) or more. 37th wettest of 40 Oxfordshire towns of 2,500+.
Rain by month
Millimetres
Sunshine by month
Hours of bright sunshine at Oxford
46 air frosts and 19 days of 25°C a year
On about 46 nights a year the air drops below freezing, and on about 1 days it stays below freezing all day. About 19 days a year reach 25°C (77°F).
Day counts are 1991–2020 averages from the Met Office’s 2 km grid. The Met Office calls a day of 25°C or more a summer day and a night below 0°C an air frost; ground frosts, on grass, come more often.
The Met Office station at Oxford
Oxford is 11 miles north of Harwell, 63 m (207 ft) above sea level. It is the nearest of the 37 long-running stations the Met Office publishes in full.
| Month | High | Low | Rain | Air frosts | Sun (hours) |
|---|---|---|---|---|---|
| January | 8.0°C | 2.4°C | 60 mm | 8.4 | 64 |
| February | 8.6°C | 2.3°C | 47 mm | 7.6 | 82 |
| March | 11.3°C | 3.6°C | 43 mm | 3.8 | 118 |
| April | 14.4°C | 5.3°C | 49 mm | 1.5 | 166 |
| May | 17.7°C | 8.2°C | 57 mm | 0.1 | 200 |
| June | 20.7°C | 11.1°C | 50 mm | 0.0 | 198 |
| July | 23.1°C | 13.1°C | 53 mm | 0.0 | 212 |
| August | 22.5°C | 13.0°C | 62 mm | 0.0 | 193 |
| September | 19.4°C | 10.7°C | 52 mm | 0.0 | 145 |
| October | 15.1°C | 8.0°C | 73 mm | 0.7 | 110 |
| November | 10.9°C | 4.9°C | 72 mm | 3.2 | 71 |
| December | 8.2°C | 2.6°C | 66 mm | 8.6 | 57 |
| Year | 15.0°C | 7.1°C | 681 mm | 34 | 1,615 |
Met Office historic station data, Oxford, 1991–2020 months averaged (a month needs 20 of the 30 years; estimated values counted, missing months left out). Sunshine: Campbell-Stokes recorder.
How Harwell compares
Against the 2,537 towns and cities of 2,500 or more across the UK, each with its own Met Office averages, and its place among Oxfordshire towns that size.
Nearby towns’ climate
The nearest towns of 1,000+ within 12 miles: a hill, a valley or the sea can make a real difference over a few miles.
| Town | July high | January low | Rain a year |
|---|---|---|---|
| Harwell | 23.1°C | 1.7°C | 618 mm |
| Didcot 2.0 mi | 23.0°C about the same | 1.8°C about the same | 630 mm |
| Chilton 2.0 mi | 22.9°C about the same | 1.4°C about the same | 645 mm |
| East Hendred 2.0 mi | 22.3°C 0.8°C cooler | 1.6°C about the same | 692 mm |
| Steventon 2.3 mi | 23.0°C about the same | 1.7°C about the same | 599 mm |
| Sutton Courtenay 2.7 mi | 23.0°C about the same | 1.9°C about the same | 620 mm |
| Drayton 3.4 mi | 22.9°C about the same | 1.8°C about the same | 614 mm |
Harwell weather by month
Average daily high and low, mean temperature and rain, 1991–2020, for the town itself (the Met Office’s HadUK-Grid).
| Month | High | Low | Mean | Rain |
|---|---|---|---|---|
| January | 7.9°C 46°F | 1.7°C 35°F | 4.8°C | 61 mm 2.4 in |
| February | 8.6°C 48°F | 1.8°C 35°F | 5.2°C | 41 mm 1.6 in |
| March | 11.3°C 52°F | 3.1°C 38°F | 7.2°C | 39 mm 1.5 in |
| April | 14.4°C 58°F | 4.6°C 40°F | 9.5°C | 46 mm 1.8 in |
| May | 17.6°C 64°F | 7.6°C 46°F | 12.6°C | 49 mm 1.9 in |
| June | 20.7°C 69°F | 10.4°C 51°F | 15.6°C | 47 mm 1.9 in |
| July | 23.1°C 74°F | 12.4°C 54°F | 17.8°C | 47 mm 1.8 in |
| August | 22.5°C 73°F | 12.4°C 54°F | 17.5°C | 54 mm 2.1 in |
| September | 19.5°C 67°F | 10.1°C 50°F | 14.8°C | 46 mm 1.8 in |
| October | 15.1°C 59°F | 7.4°C 45°F | 11.3°C | 66 mm 2.6 in |
| November | 10.9°C 52°F | 4.3°C 40°F | 7.6°C | 67 mm 2.6 in |
| December | 8.3°C 47°F | 2.0°C 36°F | 5.2°C | 57 mm 2.2 in |
| Year | 15.0°C | 6.5°C | 10.8°C | 618 mm |
Where Harwell’s numbers come from
Averages over 30 years, not a forecast.
- Mean temperature, rain and day counts: HadUK-Grid 1991–2020 averages for the Met Office 2 km grid square nearest Harwell’s centre (the town is smaller than one square).
- Highs and lows: the Met Office publishes average daily maxima and minima on its 12 km grid; each is moved by the difference between the town’s 2 km mean temperature and the 12 km square’s, which carries the town’s own height and setting over.
- Weather station and sunshine: Met Office historic station data for Oxford, 11 miles away, months of 1991–2020 averaged.
- Comparisons: every town and city of 2,500 or more across the UK, all four nations, read the same way.
Met Office HadUK-Grid · Met Office Climate Data Portal · Historic station data. Open Government Licence v3.0.
Questions about Harwell’s climate
How warm does Harwell get in summer?
July is the warmest month, with average highs of 23.1°C (74°F). About 19 days a year reach 25°C (77°F), more than 86% of UK towns.
How cold does Harwell get in winter?
January nights average 1.7°C (35°F). The air drops below freezing on about 46 nights a year, and about 1 days a year stay below freezing all day.
How much rain does Harwell get?
About 618 mm (24 in) a year, less than 89% of UK towns. November is the wettest month (67 mm) and March the driest (39 mm).
How sunny is it?
The nearest Met Office station with a sunshine record, Oxford (11 miles away), averages 1,615 hours of bright sunshine a year. Sunshine isn’t on the town grid, so this is the station’s figure.
Where do these figures come from?
The Met Office’s HadUK-Grid 1991–2020 averages, which turn thousands of weather stations into a map of the UK in 2 km squares; the page reads the squares inside Harwell. They are 30-year averages, not a forecast.
Contains Met Office data © Crown copyright 2026, Open Government Licence v3.0. HadUK-Grid 1991–2020 averages via the Met Office Climate Data Portal; station averages from Met Office historic station data. Today’s forecast for Harwell →
Contains public sector information licensed under the Open Government Licence v3.0. Contains HM Land Registry data © Crown copyright and database right 2026. Contains OS data © Crown copyright and database right 2026 (ONS boundaries). Northern Ireland: Source: NISRA; contains Land & Property Services data and Ordnance Survey of Northern Ireland information, © Crown copyright, licensed under the Open Government Licence v3.0. Scotland: contains National Records of Scotland data, Registers of Scotland data and SEPA data, © Crown copyright / © SEPA 2025, licensed under the Open Government Licence v3.0.