Frost Dates for Monrovia, CA
In Monrovia, CA, the average last spring frost is around Apr 28 and the average first fall frost around Nov 15, for a growing season of about 199 days. For frost-tender plants, wait until May 27, when the chance of frost drops to 10%.
Based on NOAA 1991–2020 records from the Mt Wilson Cbs, CA weather station, 7 miles away, elevation 5,710 ft. Frost can come earlier in low spots and valleys and later near cities and large lakes.
Frost probability by date
Chance of a 32°F frost after the spring date, or before the fall date.
| Chance | Last spring frost | First fall frost |
|---|---|---|
| 10% | May 27 | Oct 18 |
| 20% | May 17 | Oct 29 |
| 30% | May 9 | Nov 5 |
| 40% | May 2 | Nov 10 |
| 50% | Apr 28 | Nov 15 |
| 60% | Apr 22 | Nov 20 |
| 70% | Apr 15 | Nov 26 |
| 80% | Apr 9 | Dec 2 |
| 90% | Mar 31 | Dec 9 |
Light frost vs. hard freeze
Average (50%) dates for each temperature. Tender plants are damaged at 36°F; most hardy crops survive until 28°F.
| Temperature | Last in spring | First in fall |
|---|---|---|
| Light frost (36°F) | May 15 | Oct 30 |
| Frost / freeze (32°F) | Apr 28 | Nov 15 |
| Hard freeze (28°F) | Apr 8 | Dec 4 |
Planting calendar for Monrovia
Transplant May 5 – May 19
Transplant May 12 – May 26
Transplant May 12 – May 26
Transplant May 5 – May 19
Sow or transplant May 5 – May 19
Sow or transplant May 5 – May 19
Sow or transplant May 12 – May 26
Sow or transplant Mar 31 – Apr 14
Fall sowing Sep 20 – Oct 18
Fall sowing Sep 20 – Oct 11
Fall sowing Sep 6 – Sep 20
Sow or transplant Mar 31 – Apr 14
Fall sowing Sep 6 – Oct 4
Transplant Apr 14 – Apr 28
Fall sowing Aug 23 – Sep 6
Transplant Apr 7 – Apr 21
Fall sowing Aug 23 – Sep 6
Fall sowing Aug 23 – Sep 6
Fall sowing Oct 4 – Oct 25
Fall sowing Sep 6 – Sep 20
Plant Mar 31 – Apr 14
Based on the average last frost (Apr 28) and first frost (Nov 15). The dashed lines mark those dates. Seed packets list days to maturity; adjust for your varieties.