Frost dates for 85618Mammoth, AZ
The average last spring frost in Mammoth is March 13 and the average first fall frost is November 19, giving a typical growing season of about 247 days. Dates are based on NOAA 1991-2020 climate normals.
- Average last spring frost
- Mar 13
- Average first fall frost
- Nov 19
- Growing season
- 247 days
Safer after Apr 6 (1-in-10 risk)
Possible by Nov 3 (1-in-10 risk)
First frost typically in 23 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) | Mar 11 · Apr 1 · Apr 21 | Oct 24 · Nov 9 · Nov 23 | 219 days | 100% |
| Frost / freeze (32°F) | Feb 17 · Mar 13 · Apr 6 | Nov 3 · Nov 19 · Dec 4 | 247 days | 100% |
| Hard freeze (28°F) | Jan 21 · Feb 17 · Mar 13 | Nov 14 · Dec 1 · Dec 18 | 284 days | 100% |
Planting calendar for Mammoth
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 | Feb 10 – Apr 18 |
| Tomatoes | Transplant outdoors | Mar 29 – Jul 30 |
| Peppers | Start seeds indoors | Feb 10 – Mar 13 |
| Peppers | Transplant outdoors | Apr 12 – May 13 |
| Eggplant | Start seeds indoors | Feb 27 – Mar 28 |
| Eggplant | Transplant outdoors | Apr 12 – May 13 |
| Cucumbers | Sow outdoors | Apr 12 – Aug 9 |
| Summer squash | Sow outdoors | Mar 29 – May 13 |
| Winter squash & pumpkins | Sow outdoors | Apr 12 – May 13 |
| Snap beans | Sow outdoors | Mar 29 – Sep 1 |
| Sweet corn | Sow outdoors | Mar 29 – Jul 30 |
| Watermelon & cantaloupe | Sow outdoors | Apr 12 – May 13 |
| Okra | Sow outdoors | Apr 5 – Apr 28 |
| Peas | Sow outdoors (spring) | Feb 10 – Mar 28 |
| Potatoes | Plant outdoors (spring) | Feb 10 – Apr 12 |
| Onions | Start seeds indoors (spring) | Dec 30 – Jan 26 |
| Onions | Transplant outdoors (spring) | Feb 27 – Mar 28 |
| Broccoli | Start seeds indoors (spring) | Jan 23 – Feb 26 |
| Broccoli | Transplant outdoors (spring) | Feb 27 – Mar 28 |
| Broccoli | Start seeds indoors (fall) | Jul 20 – Jul 30 |
| Broccoli | Transplant outdoors (fall) | Aug 19 – Aug 30 |
| Cabbage | Start seeds indoors (spring) | Jan 13 – Feb 10 |
| Cabbage | Transplant outdoors (spring) | Feb 10 – Mar 13 |
| Cabbage | Start seeds indoors (fall) | Jul 10 – Aug 9 |
| Cabbage | Transplant outdoors (fall) | Aug 9 – Sep 9 |
| Leaf lettuce | Sow outdoors (spring) | Feb 10 – Apr 28 |
| Leaf lettuce | Sow outdoors (fall) | Aug 9 – Sep 25 |
| Spinach | Sow outdoors (spring) | Feb 3 – Mar 19 |
| Spinach | Sow outdoors (fall) | Aug 26 – Sep 30 |
| Radishes | Sow outdoors (spring) | Feb 10 – Apr 2 |
| Radishes | Sow outdoors (fall) | Aug 9 – Oct 10 |
| Kale | Sow outdoors (spring) | Feb 27 – Mar 19 |
| Kale | Sow outdoors (fall) | Aug 2 – Sep 9 |
| Carrots | Sow outdoors (spring) | Mar 13 – Apr 28 |
| Carrots | Sow outdoors (fall) | Jul 10 – Aug 25 |
| Garlic | Plant outdoors (fall) | Nov 9 – Dec 10 |
Where these dates come from
ZIP code 85618 is matched to the NOAA station San Carlos Reservoir, AZ, 52.1 km away, at 2,532 ft elevation (134 ft higher than the ZIP code's center). Nearby stations for comparison:
| Station | Elevation | Avg last frost | Avg first frost |
|---|---|---|---|
| San Carlos Reservoir, AZ (used) | 2,532 ft | Mar 13 | Nov 19 |
| San Manuel, AZ | 3,420 ft | Feb 4 | Dec 8 |
| Oracle Sp, AZ | 4,595 ft | Mar 29 | Nov 13 |
| Oracle 2 Se, AZ | 4,510 ft | Mar 23 | Nov 22 |
Frost dates near Mammoth
- San Manuel, AZ 85631 · last Feb 4, first Dec 8
- Oracle, AZ 85623 · last Mar 23, first Nov 22
- Winkelman, AZ 85192 · last Mar 13, first Nov 19
- Hayden, AZ 85135 · last Mar 13, first Nov 19
- Catalina, AZ 85738 · last Apr 2, first Nov 11
- Tucson, AZ 85739 · last Apr 2, first Nov 11
- Mount Lemmon, AZ 85619 · last Mar 23, first Nov 22
- Kearny, AZ 85137 · last Mar 13, first Nov 19
Frequently asked questions
- When is the last frost in Mammoth, AZ?
- For ZIP code 85618, the average last spring frost (32°F) is March 13, based on NOAA 1991-2020 climate normals for the San Carlos Reservoir, AZ weather station. There is a 1-in-10 chance of a frost after April 6.
- When is the first frost in Mammoth, AZ?
- The average first fall frost (32°F) is November 19. There is a 1-in-10 chance of frost by November 3, so tender plants are at risk from that point on.
- How long is the growing season in 85618?
- In half of years, the frost-free season (between the last and first 32°F frost) is at least 247 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.