Updated: 2026-08-03
That date is a benchmark for anyone planning spring planting in central London. But the real story for gardeners is rhythm: when frost arrives, how often it hits, and which years bring the hard freezes that kill young crops.
The agricultural frost season at London's St James's Park weather station (Met Office data, 1912–2025) runs through the cold half of the year. Over the full record, the average number of days with air frost (daily minimum below 0°C) in January is 6.2 days, and in February 5.4 days. That is the core of the frost season—two months that together account for the majority of freeze events in the capital.
March adds 2.5 frost days on average, which is why late spring is still risky for sensitive crops. April drops to 0.4 frost days, and May averages 0.0 frost days—essentially no measurable frost at the station in that month. The season wraps up late in the year: October shows 0.2 frost days, November 2.1, and December 4.7.
These are the events that define what a truly hard freeze looks like in central London. All temperatures are daily minimums from the Met Office MIDAS archive:
| Date | Minimum temperature (°C) |
|---|---|
| 15 February 1929 | -10.0 |
| 20 January 1940 | -9.4 |
| 24 February 1947 | -9.4 |
| 12 January 1987 | -9.0 |
| 13 January 1987 | -9.0 |
Notice that the two 1987 events are consecutive days—a reminder that hard freezes often come in waves. And the 1929 reading of -10.0°C remains the coldest the station has ever seen, well over a century into the record.
Across the 1912–2025 period, the extremes of the agricultural frost season are striking. The year with the most frost days was 1947, with 56 days below freezing and an annual minimum of -9.4°C. At the opposite end, 2003 saw just 1 frost day all year, with the coldest morning reaching only -1.8°C.
Here are the five coldest winters by annual minimum temperature, and the five mildest:
| Year | Annual minimum (°C) | Frost days that year |
|---|---|---|
| 1929 | -10.0 | 46 |
| 1940 | -9.4 | 52 |
| 1947 | -9.4 | 56 |
| 1987 | -9.0 | 31 |
| 1963 | -8.9 | 55 |
| Year | Annual minimum (°C) | Frost days that year |
|---|---|---|
| 2003 | -1.8 | 1 |
| 1961 | -1.7 | 5 |
| 1984 | -1.7 | 14 |
| 2020 | -1.2 | 3 |
| 1974 | -0.5 | 3 |
The contrast between the blocks could not be sharper. 1947 and 1963 each brought over 50 frost days to central London, while 2003—a year remembered for its summer heatwave—also had the mildest winter minimum in the series, with just a single frost day and no morning colder than -1.8°C.
For planning purposes, here is the full monthly breakdown. The "strong frost" column counts days when the minimum fell below -3°C—the threshold where unprotected tender plants typically sustain real damage.
| Month | Average frost days (min < 0°C) | Average strong frost days (min < -3°C) |
|---|---|---|
| January | 6.2 | 1.4 |
| February | 5.4 | 1.0 |
| March | 2.5 | 0.3 |
| April | 0.4 | 0.0 |
| May | 0.0 | 0.0 |
| June | 0.0 | 0.0 |
| July | 0.0 | 0.0 |
| August | 0.0 | 0.0 |
| September | 0.0 | 0.0 |
| October | 0.2 | 0.0 |
| November | 2.1 | 0.1 |
| December | 4.7 | 0.8 |
The pattern is consistent: hard freezes (below -3°C) are essentially a January and February phenomenon in London, averaging 1.4 and 1.0 days per month respectively. March strong frosts drop to 0.3 days, and from April through October the station has never logged a strong frost day on average.
The following chart shows the average number of frost days per month (minimum < 0°C). Values are in days per month.
Units: days (average per month)
January
February
March
April
May
June
July
August
September
October
November
December
Scale: width proportional to average frost days (max January at 6.2 days = 100%).
For a gardener or smallholder in central London, the practical takeaway from the full 1912–2025 series is this: the last meaningful frost risk (a day below 0°C) sits in April, with an average of 0.4 such days spread across the month. May averages at zero, but individual cold snaps are always possible—the data simply shows they are rare at this specific station.
The other practical point is year-to-year variability. 1947 produced 56 frost days; 2003 produced 1. That is not a subtle difference—it changes what you can plant and when. The mildest winters on record (2003, 1961, 1984, 2020, 1974) all had annual minimums above -2°C, meaning no hard freeze strong enough to kill woody plants outright. The coldest winters (1929, 1940, 1947, 1987, 1963) all fell below -9°C at least once.
Source: Met Office MIDAS archive, St James's Park station, London. Period analysed: 1912–2025.
HistoClima Tools: discover the weather on the day you were born, your wedding day, or your birthday-week statistics.
AI-assisted content from official Met Office data, automatically verified. 🤖 IA-assisted content · Art. 50 EU AI Act
© 2026 HistoClima · data: Met Office (OGL v3.0) · not affiliated with Met Office · citation permitted with source.