When to plant in Bostonia, CA
Planting dates worked out from Bostonia's own frost records, not a generic zone chart.
Frost is rare in Bostonia: in 14 of the last 22 springs there was none at all. Frost dates matter less here than heat, so the planting table below is left out.
Safe to plant out
Feb 1
1 year in 10 has a later frost
Average last frost
Jan 8
about a 50% chance of a later one
Average first fall frost
Dec 24
1 year in 10 by Dec 12
Frost-free days
354
median, 1991–2020
Station used: El Cajon · 2.0 km away · station 151 m, town 148 m. How we match towns to stations
Bostonia's weather over time
How the growing season has shifted here, year by year, from the station's own records.
Each year's last spring frostLong-term trend
See the data as a table
| Year | Last spring frost |
|---|---|
| 1982 | Jan 8 |
| 1983 | Jan 3 |
| 1984 | Feb 17 |
| 1985 | Feb 5 |
| 1987 | Jan 22 |
| 1988 | Mar 16 |
| 1990 | Feb 17 |
| 1993 | Jan 4 |
| 1999 | Feb 13 |
| 2000 | Jan 8 |
| 2001 | Jan 18 |
| 2002 | Feb 3 |
| 2013 | Jan 15 |
| 2019 | Jan 4 |
| 2020 | Feb 5 |
| 2022 | Feb 25 |
| 2023 | Feb 16 |
| 2024 | Jan 8 |
| 2025 | Jan 15 |
Each year's frost-free daysLong-term trend
See the data as a table
| Year | Frost-free days |
|---|---|
| 1980 | 363 |
| 1982 | 356 |
| 1983 | 327 |
| 1984 | 302 |
| 1985 | 309 |
| 1986 | 363 |
| 1990 | 308 |
| 1993 | 352 |
| 1995 | 363 |
| 2000 | 356 |
| 2009 | 363 |
| 2010 | 328 |
| 2011 | 338 |
| 2012 | 352 |
| 2013 | 349 |
| 2014 | 363 |
| 2015 | 359 |
| 2016 | 350 |
| 2017 | 354 |
| 2018 | 361 |
| 2019 | 360 |
| 2020 | 328 |
| 2021 | 363 |
| 2022 | 294 |
| 2023 | 317 |
| 2024 | 356 |
| 2025 | 349 |
Each year's average temperature, April to SeptemberLong-term trend
See the data as a table
| Year | Growing-season temperature |
|---|---|
| 1980 | 21.3 °C |
| 1982 | 21.3 °C |
| 1983 | 21.7 °C |
| 1986 | 21.2 °C |
| 1995 | 20.8 °C |
| 1999 | 20.7 °C |
| 2000 | 22.4 °C |
| 2001 | 21.8 °C |
| 2006 | 22.8 °C |
| 2008 | 22.5 °C |
| 2010 | 20.8 °C |
| 2011 | 21.0 °C |
| 2012 | 21.6 °C |
| 2013 | 21.6 °C |
| 2014 | 22.8 °C |
| 2015 | 22.4 °C |
| 2016 | 22.2 °C |
| 2017 | 22.3 °C |
| 2018 | 22.4 °C |
| 2019 | 21.5 °C |
| 2020 | 22.6 °C |
| 2021 | 22.1 °C |
| 2022 | 22.1 °C |
| 2023 | 20.7 °C |
| 2024 | 21.4 °C |
| 2025 | 21.3 °C |
| 2026 | 22.5 °C |
What this means for you: This station's record is too short to show a reliable trend yet.
Source: daily records from El Cajon (NOAA GHCN-Daily). Years with too many missing days are left out.