Photo: David Howard · CC BY-SA 2.0Grendon Underwood is among the frostiest of UK towns
A warm July spell here typically peaks at 22.5°C (73°F). Wet weather is most frequent in October and least in March. About 17 days a year reach 25°C, more than in 80% of UK towns. Long walks are most pleasant from June to September, when afternoons reach 19–23°C.
Met Office 1991–2020 averages for the town itself.
A year in Grendon Underwood at a glance
Each month’s typical high and low, in °C.
What a year in Grendon Underwood feels like
Typical highs and lows by season and by month, from the Met Office’s 1991–2020 averages.
About 654 mm of rain a year
October is the wettest month and March the driest. About 16 days a year bring 10 mm (0.4 in) or more.
Rain by month
Millimetres
Sunshine by month
Hours of bright sunshine at Oxford
A frosty town: 59 air frosts and 17 days of 25°C a year
On about 59 nights a year the air drops below freezing, and on about 1 days it stays below freezing all day. About 17 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 14 miles south-west of Grendon Underwood, 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 Grendon Underwood 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 Buckinghamshire 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 |
|---|---|---|---|
| Grendon Underwood | 22.5°C | 1.0°C | 654 mm |
| Calvert 2.4 mi | 22.4°C about the same | 0.9°C about the same | 665 mm |
| Quainton 3.6 mi | 22.4°C about the same | 1.0°C about the same | 674 mm |
| Waddesdon 4.2 mi | 22.9°C about the same | 1.1°C about the same | 641 mm |
| Steeple Claydon 4.2 mi | 22.4°C about the same | 1.0°C about the same | 663 mm |
| Ambrosden 4.9 mi | 22.8°C about the same | 1.2°C about the same | 651 mm |
| Upper Arncott 5.1 mi | 22.8°C about the same | 1.3°C about the same | 649 mm |
Grendon Underwood 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 | 7.4°C 45°F | 1.0°C 34°F | 4.2°C | 65 mm 2.5 in |
| February | 8.1°C 47°F | 1.1°C 34°F | 4.6°C | 45 mm 1.8 in |
| March | 10.8°C 51°F | 2.2°C 36°F | 6.5°C | 39 mm 1.5 in |
| April | 13.9°C 57°F | 3.8°C 39°F | 8.8°C | 46 mm 1.8 in |
| May | 17.1°C 63°F | 6.6°C 44°F | 11.8°C | 55 mm 2.2 in |
| June | 20.1°C 68°F | 9.4°C 49°F | 14.7°C | 48 mm 1.9 in |
| July | 22.5°C 73°F | 11.5°C 53°F | 17.0°C | 50 mm 2.0 in |
| August | 22.1°C 72°F | 11.3°C 52°F | 16.7°C | 58 mm 2.3 in |
| September | 19.0°C 66°F | 8.8°C 48°F | 13.9°C | 51 mm 2.0 in |
| October | 14.8°C 59°F | 6.4°C 44°F | 10.6°C | 69 mm 2.7 in |
| November | 10.5°C 51°F | 3.5°C 38°F | 7.0°C | 67 mm 2.6 in |
| December | 7.9°C 46°F | 1.3°C 34°F | 4.6°C | 61 mm 2.4 in |
| Year | 14.5°C | 5.6°C | 10.0°C | 654 mm |
Where Grendon Underwood’s numbers come from
Averages over 30 years, not a forecast.
- Mean temperature, rain and day counts: HadUK-Grid 1991–2020 averages for the 1 Met Office 2 km grid square whose centre lies inside Grendon Underwood’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 Oxford, 14 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 Grendon Underwood’s climate
How warm does Grendon Underwood get in summer?
July is the warmest month, with average highs of 22.5°C (73°F). About 17 days a year reach 25°C (77°F), more than 80% of UK towns.
How cold does Grendon Underwood get in winter?
January nights average 1.0°C (34°F). The air drops below freezing on about 59 nights a year, and about 1 days a year stay below freezing all day.
How much rain does Grendon Underwood get?
About 654 mm (26 in) a year, less than 79% of UK towns. October is the wettest month (69 mm) and March the driest (39 mm).
How sunny is it?
The nearest Met Office station with a sunshine record, Oxford (14 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 Grendon Underwood. 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 Grendon Underwood →
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