Photo: Peter Trimming · CC BY-SA 2.0More days reach 25 degrees in South Merstham than in 78% of UK towns
In January the night’s low is typically 1.9°C (35°F). Winters are mild: January nights here are milder than in 63% of UK towns. Of all months, November brings the most rain and March the least. Expect about 43 frosty starts a year, nights when the air falls below freezing.
Met Office 1991–2020 averages for the town itself.
A year in South Merstham at a glance
Each month’s typical high and low, in °C.
What a year in South Merstham feels like
Typical highs and lows by season and by month, from the Met Office’s 1991–2020 averages.
About 808 mm of rain a year
November is the wettest month and March the driest. About 23 days a year bring 10 mm (0.4 in) or more. 10th wettest of 66 Surrey towns of 2,500+.
Rain by month
Millimetres
Sunshine by month
Hours of bright sunshine at Heathrow
43 air frosts and 16 days of 25°C a year
On about 43 nights a year the air drops below freezing, and on about under 1 days it stays below freezing all day. About 16 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 20 miles north-west of South Merstham, 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 South Merstham 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 Surrey 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 |
|---|---|---|---|
| South Merstham | 22.3°C | 1.9°C | 808 mm |
| Redhill 1.9 mi | 22.9°C 0.6°C warmer | 1.4°C 0.5°C colder | 762 mm |
| Netherne on-the-Hill 2.3 mi | 22.0°C about the same | 2.0°C about the same | 845 mm |
| South Nutfield 2.3 mi | 22.2°C about the same | 1.7°C about the same | 788 mm |
| Hooley 2.3 mi | 22.0°C about the same | 2.0°C about the same | 845 mm |
| Chaldon 2.4 mi | 22.1°C about the same | 1.6°C about the same | 847 mm |
| Bletchingley 2.4 mi | 22.2°C about the same | 1.6°C about the same | 789 mm |
South Merstham 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 | 7.8°C 46°F | 1.9°C 35°F | 4.8°C | 87 mm 3.4 in |
| February | 8.1°C 47°F | 1.6°C 35°F | 4.8°C | 64 mm 2.5 in |
| March | 10.8°C 51°F | 3.0°C 37°F | 6.9°C | 50 mm 2.0 in |
| April | 14.0°C 57°F | 4.6°C 40°F | 9.3°C | 52 mm 2.0 in |
| May | 17.2°C 63°F | 7.4°C 45°F | 12.3°C | 52 mm 2.0 in |
| June | 20.2°C 68°F | 10.2°C 50°F | 15.2°C | 52 mm 2.0 in |
| July | 22.3°C 72°F | 12.4°C 54°F | 17.4°C | 57 mm 2.2 in |
| August | 21.7°C 71°F | 12.3°C 54°F | 17.3°C | 62 mm 2.4 in |
| September | 19.0°C 66°F | 9.9°C 50°F | 14.5°C | 61 mm 2.4 in |
| October | 14.8°C 59°F | 7.6°C 46°F | 11.2°C | 90 mm 3.5 in |
| November | 10.8°C 51°F | 4.4°C 40°F | 7.6°C | 92 mm 3.6 in |
| December | 8.1°C 47°F | 2.2°C 36°F | 5.1°C | 90 mm 3.5 in |
| Year | 14.6°C | 6.4°C | 10.5°C | 808 mm |
Where South Merstham’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 South Merstham’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), 20 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 South Merstham’s climate
How warm does South Merstham get in summer?
July is the warmest month, with average highs of 22.3°C (72°F). About 16 days a year reach 25°C (77°F), more than 78% of UK towns.
How cold does South Merstham get in winter?
February nights average 1.6°C (35°F). The air drops below freezing on about 43 nights a year, and about under 1 days a year stay below freezing all day.
How much rain does South Merstham get?
About 808 mm (32 in) a year, more than 56% of UK towns. November is the wettest month (92 mm) and March the driest (50 mm).
How sunny is it?
The nearest Met Office station with a sunshine record, Heathrow (20 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 South Merstham. 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 South Merstham →
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