Humboldt, AZ frost dates
Last spring frostApr 30median date
First fall frostOct 20median date
Growing season173 daysfrost-free
Hardiness zone8aZone 8a
How Humboldt compares
- In 8 years out of 10, the last spring frost in Humboldt falls between April 14 and May 15, a 31-day window. The first fall frost falls between October 7 and November 4.
- The median last frost is 14 days later than the Arizona median of Apr 16.
- Its 173-day growing season is longer than 36% of the 193 Arizona places with a regular frost season (state median 197 days).
- The last frost is 32 days later than the zone 8a median of Mar 29. Hardiness zones measure winter cold, not season length, so use these dates rather than a zone 8a chart.
- The weather station records an average of 128 nights a year at or below 32°F.
- Compared with Flagstaff, AZ, 94 km away, the last frost here is 35 days earlier than there and the growing season is 57 days longer.
Frost probability
| Chance of frost after | Date |
|---|---|
| 90% (early) | April 14 |
| 50% (median) | April 30 |
| 10% (safe for tender plants) | May 15 |
| Chance of frost before | Date |
|---|---|
| 10% (early) | October 7 |
| 50% (median) | October 20 |
| 90% (late) | November 4 |
Frost here means 32°F (0°C). A median date means half of years have their last frost earlier and half later.
Planting calendar for Humboldt, AZ
Humboldt, AZ frost dates — last frost Apr 30, first frost Oct 20, zone 8a. whenisthelastfrost.com
Crop
JFMAMJJASOND
Start indoors: Feb 5 to Feb 19Transplant outside: Apr 2 to Apr 16
Start indoors: Feb 19 to Mar 5Transplant outside: May 14 to May 28
Start indoors: Feb 19 to Mar 5Transplant outside: May 14 to May 28
Start indoors: Mar 5 to Mar 19Transplant outside: May 7 to May 21
Start indoors: Mar 5 to Mar 19Transplant outside: Apr 9 to Apr 23Sow outdoors: Apr 2 to May 7Plant for fall: Aug 25 to Sep 22
Start indoors: Mar 5 to Mar 19Transplant outside: Apr 2 to Apr 16Sow outdoors: Apr 2 to Apr 16Plant for fall: Aug 11 to Sep 1
Start indoors: Mar 5 to Mar 19Transplant outside: Apr 16 to Apr 30Plant for fall: Jul 14 to Aug 4
Start indoors: Mar 5 to Mar 19Transplant outside: Apr 9 to Apr 23Plant for fall: Jul 14 to Aug 4
Start indoors: Mar 5 to Mar 19Transplant outside: Apr 16 to Apr 30Plant for fall: Jul 14 to Aug 4
Start indoors: Mar 19 to Apr 2Transplant outside: May 21 to Jun 4Sow outdoors: May 21 to Jun 4
Start indoors: Mar 19 to Apr 2Transplant outside: May 7 to May 21
Sow outdoors: Mar 19 to Apr 9Plant for fall: Jul 28 to Aug 18
Sow outdoors: Mar 19 to Apr 9Plant for fall: Aug 25 to Sep 15
Sow outdoors: Mar 26 to May 7Plant for fall: Sep 8 to Sep 29
Start indoors: Apr 2 to Apr 9Transplant outside: May 14 to May 21Sow outdoors: May 7 to May 21Plant for fall: Aug 4 to Aug 18
Start indoors: Apr 2 to Apr 9Sow outdoors: May 7 to May 21Plant for fall: Aug 11 to Aug 25
Start indoors: Apr 2 to Apr 9Sow outdoors: May 7 to May 21
Start indoors: Apr 2 to Apr 9Transplant outside: May 14 to May 28
Sow outdoors: Apr 9 to May 7Plant for fall: Jul 28 to Aug 11
Sow outdoors: Apr 9 to May 7Plant for fall: Aug 11 to Aug 25
Sow outdoors: Apr 9 to Apr 30
Sow outdoors: Apr 16 to May 14Plant for fall: Aug 11 to Aug 25
Sow outdoors: Apr 16 to May 7Plant for fall: Aug 25 to Sep 15
Sow outdoors: May 7 to May 28Plant for fall: Aug 4 to Aug 18
Sow outdoors: May 7 to May 21
Transplant outside: May 14 to Jun 4
Plant for fall: Oct 6 to Nov 10
Start indoorsTransplant outsideSow outdoorsPlant for fallMedian frost dates
When to plant vegetables in Humboldt, AZ
| Crop | Start indoors | Transplant | Sow outdoors | Fall crop |
|---|---|---|---|---|
| Onions | Feb 5 – Feb 19 | Apr 2 – Apr 16 | — | — |
| Peppers | Feb 19 – Mar 5 | May 14 – May 28 | — | — |
| Eggplant | Feb 19 – Mar 5 | May 14 – May 28 | — | — |
| Tomatoes | Mar 5 – Mar 19 | May 7 – May 21 | — | — |
| Lettuce | Mar 5 – Mar 19 | Apr 9 – Apr 23 | Apr 2 – May 7 | Aug 25 – Sep 22 |
| Kale | Mar 5 – Mar 19 | Apr 2 – Apr 16 | Apr 2 – Apr 16 | Aug 11 – Sep 1 |
| Broccoli | Mar 5 – Mar 19 | Apr 16 – Apr 30 | — | Jul 14 – Aug 4 |
| Cabbage | Mar 5 – Mar 19 | Apr 9 – Apr 23 | — | Jul 14 – Aug 4 |
| Cauliflower | Mar 5 – Mar 19 | Apr 16 – Apr 30 | — | Jul 14 – Aug 4 |
| Okra | Mar 19 – Apr 2 | May 21 – Jun 4 | May 21 – Jun 4 | — |
| Basil | Mar 19 – Apr 2 | May 7 – May 21 | — | — |
| Peas | — | — | Mar 19 – Apr 9 | Jul 28 – Aug 18 |
| Spinach | — | — | Mar 19 – Apr 9 | Aug 25 – Sep 15 |
| Radishes | — | — | Mar 26 – May 7 | Sep 8 – Sep 29 |
| Cucumbers | Apr 2 – Apr 9 | May 14 – May 21 | May 7 – May 21 | Aug 4 – Aug 18 |
| Zucchini & Summer Squash | Apr 2 – Apr 9 | — | May 7 – May 21 | Aug 11 – Aug 25 |
| Winter Squash & Pumpkins | Apr 2 – Apr 9 | — | May 7 – May 21 | — |
| Melons & Watermelon | Apr 2 – Apr 9 | May 14 – May 28 | — | — |
| Carrots | — | — | Apr 9 – May 7 | Jul 28 – Aug 11 |
| Beets | — | — | Apr 9 – May 7 | Aug 11 – Aug 25 |
| Potatoes | — | — | Apr 9 – Apr 30 | — |
| Swiss Chard | — | — | Apr 16 – May 14 | Aug 11 – Aug 25 |
| Cilantro | — | — | Apr 16 – May 7 | Aug 25 – Sep 15 |
| Green Beans | — | — | May 7 – May 28 | Aug 4 – Aug 18 |
| Sweet Corn | — | — | May 7 – May 21 | — |
| Sweet Potatoes | — | May 14 – Jun 4 | — | — |
| Garlic | — | — | — | Oct 6 – Nov 10 |
Dates come from the median frost dates and common extension-service timing. Adjust for your soil temperature, microclimate and the varieties you grow.
About these dates
Based on 1991–2020 NOAA climate normals for the Prescott, AZ weather station, 19 km away (elevation 5,207 ft (1,587 m)).
Frost dates near Humboldt
- Dewey Apr 30 · Oct 20
- Mayer Apr 5 · Nov 17
- Prescott Valley Apr 20 · Oct 27
- Prescott Apr 30 · Oct 20
- Sedona (Yavapai) Apr 20 · Oct 27
- Jerome Mar 26 · Nov 25
- Cottonwood Mar 30 · Nov 10
- Crown King Apr 5 · Nov 17
- Clarkdale Mar 30 · Nov 10
- Camp Verde Apr 16 · Oct 30
Frequently asked questions
When is the last frost in Humboldt, AZ?
The median last spring frost in Humboldt, AZ is April 30. There is still about a 10% chance of frost after May 15, so wait until then to plant frost-tender crops like tomatoes and peppers.
When is the first frost in Humboldt, AZ?
The median first fall frost is October 20, with about a 10% chance of frost before October 7.
How long is the growing season in Humboldt, AZ?
About 173 days between the median last spring frost and first fall frost.
What planting zone is Humboldt, AZ?
Humboldt, AZ is in USDA hardiness zone 8a.