Winter nights in Harpenden are colder than in 73% of UK towns
Sunny July days climb to about 22.2°C (72°F). By warm days alone, it ranks hotter than 71% of UK towns. The gap between a January night and a July afternoon is 21°C. The heating season runs November to April: each of those months averages under 10°C.
Met Office 1991–2020 averages for the town itself.
A year in Harpenden at a glance
Each month’s typical high and low, in °C.
What a year in Harpenden feels like
Typical highs and lows by season and by month, from the Met Office’s 1991–2020 averages.
About 710 mm of rain a year
October is the wettest month and March the driest. About 18 days a year bring 10 mm (0.4 in) or more. 7th wettest of 50 Hertfordshire towns of 2,500+.
Rain by month
Millimetres
Sunshine by month
Hours of bright sunshine at Heathrow
43 air frosts and 15 days of 25°C a year
On about 43 nights a year the air drops below freezing, and on about 2 days it stays below freezing all day. About 15 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 Heathrow
Heathrow is 24 miles south of Harpenden, 25 m (82 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 | 8.4°C | 2.7°C | 59 mm | 6.8 | 59 |
| February | 9.0°C | 2.6°C | 45 mm | 6.2 | 76 |
| March | 11.7°C | 4.1°C | 39 mm | 3.0 | 120 |
| April | 15.0°C | 6.0°C | 42 mm | 0.8 | 169 |
| May | 18.4°C | 9.1°C | 46 mm | 0.0 | 197 |
| June | 21.6°C | 12.0°C | 47 mm | 0.0 | 197 |
| July | 23.9°C | 14.2°C | 46 mm | 0.0 | 206 |
| August | 23.4°C | 14.1°C | 54 mm | 0.0 | 192 |
| September | 20.2°C | 11.6°C | 50 mm | 0.0 | 150 |
| October | 15.8°C | 8.8°C | 65 mm | 0.3 | 111 |
| November | 11.5°C | 5.3°C | 67 mm | 2.7 | 68 |
| December | 8.8°C | 3.1°C | 57 mm | 7.2 | 53 |
| Year | 15.6°C | 7.8°C | 616 mm | 27 | 1,597 |
Met Office historic station data, Heathrow (London Airport), 1991–2020 months averaged (a month needs 20 of the 30 years; estimated values counted, missing months left out). Sunshine: Kipp & Zonen recorder.
How Harpenden 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 Hertfordshire 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 |
|---|---|---|---|
| Harpenden | 22.2°C | 1.5°C | 710 mm |
| Redbourn 2.5 mi | 22.2°C about the same | 1.5°C about the same | 718 mm |
| Wheathampstead 2.6 mi | 22.4°C about the same | 1.5°C about the same | 676 mm |
| Kimpton 3.2 mi | 22.4°C about the same | 1.5°C about the same | 688 mm |
| Sandridge 3.2 mi | 22.4°C about the same | 1.7°C about the same | 704 mm |
| Flamstead 3.7 mi | 22.2°C about the same | 1.4°C about the same | 722 mm |
| Slip End 4.3 mi | 22.3°C about the same | 1.5°C about the same | 725 mm |
Harpenden 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 | 7.1°C 45°F | 1.5°C 35°F | 4.3°C | 67 mm 2.6 in |
| February | 7.7°C 46°F | 1.5°C 35°F | 4.6°C | 51 mm 2.0 in |
| March | 10.4°C 51°F | 2.8°C 37°F | 6.6°C | 42 mm 1.7 in |
| April | 13.6°C 56°F | 4.4°C 40°F | 9.0°C | 50 mm 2.0 in |
| May | 16.8°C 62°F | 7.2°C 45°F | 12.0°C | 51 mm 2.0 in |
| June | 19.7°C 68°F | 10.1°C 50°F | 14.9°C | 54 mm 2.1 in |
| July | 22.2°C 72°F | 12.2°C 54°F | 17.2°C | 52 mm 2.1 in |
| August | 21.9°C 71°F | 12.2°C 54°F | 17.1°C | 67 mm 2.6 in |
| September | 18.8°C 66°F | 10.0°C 50°F | 14.4°C | 55 mm 2.2 in |
| October | 14.4°C 58°F | 7.4°C 45°F | 10.9°C | 77 mm 3.0 in |
| November | 10.2°C 50°F | 4.1°C 39°F | 7.2°C | 77 mm 3.0 in |
| December | 7.5°C 46°F | 1.9°C 35°F | 4.7°C | 68 mm 2.7 in |
| Year | 14.2°C | 6.3°C | 10.2°C | 710 mm |
Where Harpenden’s numbers come from
Averages over 30 years, not a forecast.
- Mean temperature, rain and day counts: HadUK-Grid 1991–2020 averages for the 2 Met Office 2 km grid squares whose centre lies inside Harpenden’s built-up area.
- 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 Heathrow (London Airport), 24 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 Harpenden’s climate
How warm does Harpenden get in summer?
July is the warmest month, with average highs of 22.2°C (72°F). About 15 days a year reach 25°C (77°F), more than 71% of UK towns.
How cold does Harpenden get in winter?
February nights average 1.5°C (35°F). The air drops below freezing on about 43 nights a year, and about 2 days a year stay below freezing all day.
How much rain does Harpenden get?
About 710 mm (28 in) a year, less than 63% of UK towns. October is the wettest month (77 mm) and March the driest (42 mm).
How sunny is it?
The nearest Met Office station with a sunshine record, Heathrow (24 miles away), averages 1,597 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 Harpenden. 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 Harpenden →
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.