Frost dates for 92378Rimforest, CA
The average last spring frost in Rimforest is May 5 and the average first fall frost is November 2, giving a typical growing season of about 176 days. Dates are based on NOAA 1991-2020 climate normals.
- Average last spring frost
- May 5
- Average first fall frost
- Nov 2
- Growing season
- 176 days
Safer after May 31 (1-in-10 risk)
Possible by Oct 12 (1-in-10 risk)
First frost typically in 4 days
Frost risk by date
NOAA reports frost dates as probabilities. The middle date is the average (a 50% chance). For spring, the 10% date is a safer planting date: frost after it happens in about 1 year in 10. Light frost (36°F) can damage tender plants; a hard freeze (28°F) kills most annuals.
| Temperature | Last spring: 90% / 50% / 10% chance | First fall: 10% / 50% / 90% chance | Growing season (50%) | Years with at least one |
|---|---|---|---|---|
| Light frost (36°F) | May 3 · May 27 · Jun 10 | Sep 30 · Oct 18 · Nov 5 | 145 days | 100% |
| Frost / freeze (32°F) | Apr 9 · May 5 · May 31 | Oct 12 · Nov 2 · Nov 15 | 176 days | 100% |
| Hard freeze (28°F) | Mar 14 · Apr 11 · May 12 | Oct 31 · Nov 16 · Nov 30 | 215 days | 100% |
Planting calendar for Rimforest
Planting windows from the University of Maryland Extension calendar, shifted to your average frost dates. Use them as a starting point and adjust for seed packet instructions and local conditions.
| Crop | Task | Window |
|---|---|---|
| Tomatoes | Start seeds indoors | Apr 4 – Jun 10 |
| Tomatoes | Transplant outdoors | May 21 – Jul 13 |
| Peppers | Start seeds indoors | Apr 4 – May 5 |
| Peppers | Transplant outdoors | Jun 4 – Jul 5 |
| Eggplant | Start seeds indoors | Apr 21 – May 20 |
| Eggplant | Transplant outdoors | Jun 4 – Jul 5 |
| Cucumbers | Sow outdoors | Jun 4 – Jul 23 |
| Summer squash | Sow outdoors | May 21 – Jul 5 |
| Winter squash & pumpkins | Sow outdoors | Jun 4 – Jul 5 |
| Snap beans | Sow outdoors | May 21 – Aug 15 |
| Sweet corn | Sow outdoors | May 21 – Jul 13 |
| Watermelon & cantaloupe | Sow outdoors | Jun 4 – Jul 5 |
| Okra | Sow outdoors | May 28 – Jun 20 |
| Peas | Sow outdoors (spring) | Apr 4 – May 20 |
| Potatoes | Plant outdoors (spring) | Apr 4 – Jun 4 |
| Onions | Start seeds indoors (spring) | Feb 21 – Mar 20 |
| Onions | Transplant outdoors (spring) | Apr 21 – May 20 |
| Broccoli | Start seeds indoors (spring) | Mar 17 – Apr 20 |
| Broccoli | Transplant outdoors (spring) | Apr 21 – May 20 |
| Broccoli | Start seeds indoors (fall) | Jul 3 – Jul 13 |
| Broccoli | Transplant outdoors (fall) | Aug 2 – Aug 13 |
| Cabbage | Start seeds indoors (spring) | Mar 7 – Apr 4 |
| Cabbage | Transplant outdoors (spring) | Apr 4 – May 5 |
| Cabbage | Start seeds indoors (fall) | Jun 23 – Jul 23 |
| Cabbage | Transplant outdoors (fall) | Jul 23 – Aug 23 |
| Leaf lettuce | Sow outdoors (spring) | Apr 4 – Jun 20 |
| Leaf lettuce | Sow outdoors (fall) | Jul 23 – Sep 8 |
| Spinach | Sow outdoors (spring) | Mar 28 – May 11 |
| Spinach | Sow outdoors (fall) | Aug 9 – Sep 13 |
| Radishes | Sow outdoors (spring) | Apr 4 – May 25 |
| Radishes | Sow outdoors (fall) | Jul 23 – Sep 23 |
| Kale | Sow outdoors (spring) | Apr 21 – May 11 |
| Kale | Sow outdoors (fall) | Jul 16 – Aug 23 |
| Carrots | Sow outdoors (spring) | May 5 – Jun 20 |
| Carrots | Sow outdoors (fall) | Jun 23 – Aug 8 |
| Garlic | Plant outdoors (fall) | Oct 23 – Nov 23 |
Where these dates come from
ZIP code 92378 is matched to the NOAA station Lake Arrowhead, CA, 3.9 km away, at 5,205 ft elevation (425 ft lower than the ZIP code's center). Nearby stations for comparison:
| Station | Elevation | Avg last frost | Avg first frost |
|---|---|---|---|
| Lake Arrowhead, CA (used) | 5,205 ft | May 5 | Nov 2 |
| Hesperia 2E, CA | 3,055 ft | Feb 28 | Dec 1 |
| Redlands, CA | 1,410 ft | Jan 27 | Dec 19 |
| Big Bear Lake, CA | 6,753 ft | May 27 | Oct 4 |
Frost dates near Rimforest
- Twin Peaks, CA 92391 · last May 5, first Nov 2
- Lake Arrowhead, CA 92352 · last May 5, first Nov 2
- Skyforest, CA 92385 · last May 5, first Nov 2
- Crestline, CA 92325 · last May 5, first Nov 2
- Cedar Glen, CA 92321 · last May 5, first Nov 2
- Cedarpines Park, CA 92322 · last May 5, first Nov 2
- San Bernardino, CA 92404 · last Jan 27, first Dec 19
- Patton, CA 92369 · last Jan 27, first Dec 19
Frequently asked questions
- When is the last frost in Rimforest, CA?
- For ZIP code 92378, the average last spring frost (32°F) is May 5, based on NOAA 1991-2020 climate normals for the Lake Arrowhead, CA weather station. There is a 1-in-10 chance of a frost after May 31.
- When is the first frost in Rimforest, CA?
- The average first fall frost (32°F) is November 2. There is a 1-in-10 chance of frost by October 12, so tender plants are at risk from that point on.
- How long is the growing season in 92378?
- In half of years, the frost-free season (between the last and first 32°F frost) is at least 176 days long.
- Are these frost dates a forecast?
- No. They are 30-year averages and probabilities from NOAA weather station records. Use them to plan, then watch your local forecast before planting tender crops or leaving them uncovered.