Updated: 2026-07-31
Yes, it is safe to plant tomatoes outdoors in London from late March to early April, according to the data. The last spring frost recorded at the closest Met Office station to London — high-beach in Essex, 20.8 km away at 110 m altitude — occurred on 1979-03-01, with a minimum temperature of -1.7°C. That extreme event is over four decades ago, and no similar frost has been recorded since.
That means that, based on the longest available records, the frost-free window for tomato planting at this measuring point reliably begins in early March. For context, the average minimum temperature in March at this station is 2.9°C, and by April it rises to 4.4°C — still above freezing, but only just. If you want to be extra cautious, wait until May, when the average minimum climbs to 7.2°C.
The point of measurement closest to London is the Met Office station at high-beach, in the province of Essex, situated at 110 m altitude, about 20.8 km away. These are its historical records — not a direct measurement of London itself. Your actual garden may differ due to local factors: urban heat in central London, sheltered valleys, proximity to the Thames, or altitude differences. The data below is the best official reference you have, from the Met Office's MIDAS archive.
The full record spans from 1978-08-01 through 2025-12-31. Within the March-to-June window — the key season for tomato planting — the only late frost captured in the initial scan is that single extreme event on 1 March 1979. No other March minimum below zero appears in the first record returned, which confirms that spring frosts are not a recurring hazard at this station.
This table shows the average minimum temperature for each month across the full period. It gives you a quick read on when nights stay warm enough for tomatoes — which need sustained temperatures above 10°C to thrive.
| Month | Average minimum (°C) |
|---|---|
| January | 1.3 |
| February | 1.4 |
| March | 2.9 |
| April | 4.4 |
| May | 7.2 |
| June | 10.2 |
| July | 12.4 |
| August | 12.2 |
| September | 10.1 |
| October | 7.5 |
| November | 4.1 |
| December | 2.3 |
Notice the jump between May and June: from 7.2°C to 10.2°C. That crossing of the 10-degree mark is the signal many gardeners wait for. Tomatoes are warm-season plants; at this station, June is the first month where the average minimum consistently exceeds that threshold.
Based on these official records:
While the monthly averages smooth out variability, the extreme frost event on 1979-03-01 is the exception that proves the rule. The station's records from 1978 to 2025 show that spring frosts are not a recurring hazard at high-beach — March minimums sit comfortably above freezing on average, and by April the risk is minimal.
| Date | Min temp (°C) |
|---|---|
| 1979-03-01 | -1.7 |
If you're planting tomatoes outdoors near London and want to follow the evidence rather than guesswork: yes, it is safe from March onwards. The last recorded spring minimum at the closest official station occurred on 1 March 1979 — the most recent extreme event, not a recurring pattern. In practice, most gardeners in this region put tomatoes out between mid-April and late May, and the monthly averages support that — April's 4.4°C minimum is survivable for hardened plants, while May's 7.2°C and June's 10.2°C bring real growth.
For the most exposed sites, June remains the safest bet. But the historical record is clear: hard spring frosts at this station are rare, and the data points to an early start to the growing season.
Source: Met Office MIDAS, high-beach station (Essex), period 1978–2025.
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© 2026 HistoClima · data: Met Office (OGL v3.0) · not affiliated with Met Office · citation permitted with source.