Caldwell, Idaho planting calendar and frost dates
Caldwell is in USDA hardiness zone 7a. The last spring frost typically comes around April 29 and the first fall frost around October 13, giving about 164 frost-free days a year.
- Hardiness zone
- Zone 7a
- Typical last frost
- April 29
- Typical first frost
- October 13
- Frost-free season
- 164 days
Frost dates in Caldwell
Last spring frost
- April 15Risky: frost later than this in 9 years out of 10
- April 29Typical: a later frost in half of years
- May 18Safe: a later frost only 1 year in 10
First fall frost
- September 29Risky: frost earlier than this 1 year in 10
- October 13Typical: an earlier frost in half of years
- October 28Late: frost before this in 9 years out of 10
The growing season between the typical last and first frosts is about 164 days. Frost here means a low of 32°F at the weather station. A hard freeze (28°F), which damages most hardy crops too, typically ends around April 11 and returns around October 25.
NOAA U.S. Climate Normals 1991-2020 for Nampa Sugar Factory, 5.6 miles SE of the city center. Low-lying and rural spots often frost later in spring and earlier in fall than airports and city centers.
What to plant each month in Caldwell
January
Start indoors: onions
February
Start indoors: broccoli, cabbages, cauliflower, collard greens, kale, leeks, onions, oregano, parsley, petunias, ranunculus, rosemary, snapdragons
March
Start indoors: basil, black-eyed susans, broccoli, cabbages, cauliflower, celery, chives, cilantro, collard greens, eggplants, ginger, leeks, lettuce, marigolds, nasturtiums, oregano, parsley, peppers, petunias, ranunculus, rosemary, sage, snapdragons, spinach, swiss chard, tomatoes
Plant or sow outdoors: black-eyed susans, blueberries, garlic, grapes, grass seed, hollyhocks, kale, onions, peas, poppies, raspberries, rhubarb, strawberries, turnips, wildflowers
April
Start indoors: basil, cantaloupes, cilantro, cosmos, cucumbers, marigolds, nasturtiums, okra, pumpkins, ranunculus, tomatoes, watermelons, winter squash, zucchini
Plant or sow outdoors: asparagus, beets, black-eyed susans, blackberries, blueberries, broccoli, cabbages, carrots, cauliflower, chives, cilantro, collard greens, dahlias, dill, figs, garden mums, garlic, gladioli, grapes, grass seed, green onions, hollyhocks, kale, lavenders, leeks, lettuce, lilies, marigolds, mints, nasturtiums, onions, oregano, parsley, peas, petunias, poppies, potatoes, radishes, ranunculus, raspberries, rhubarb, rosemary, roses, sage, snapdragons, spinach, strawberries, sunflowers, sweet corn, swiss chard, thyme, turnips, wildflowers
May
Start indoors: cosmos, cucumbers, okra, pumpkins, winter squash, zinnias, zucchini
Plant or sow outdoors: asparagus, basil, cantaloupes, chives, cilantro, cucumbers, dahlias, dill, eggplants, garden mums, ginger, gladioli, grapes, green beans, green onions, kentucky bluegrass, lavenders, lettuce, lilies, marigolds, mints, nasturtiums, oregano, parsley, peppers, perennial ryegrass, petunias, pumpkins, ranunculus, rosemary, sage, spinach, sunflowers, sweet corn, sweet peas, swiss chard, tall fescue, thyme, tomatoes, watermelons, winter squash, zucchini
June
Start indoors: zinnias
Plant or sow outdoors: bermudagrass, cantaloupes, celery, centipedegrass, cosmos, cucumbers, eggplants, green beans, green onions, okra, peanuts, peppers, pumpkins, st. augustinegrass, sweet potatoes, tomatoes, watermelons, winter squash, zinnias, zoysiagrass, zucchini
July
Plant or sow outdoors: bermudagrass, centipedegrass, st. augustinegrass, zinnias, zoysiagrass
Plant for fall: bearded irises, broccoli, brussels sprouts, carrots, collard greens, lettuce, peas, snapdragons, swiss chard
August
Plant for fall: azaleas, bearded irises, beets, broccoli, cabbages, carrots, cauliflower, clematis, collard greens, coneflowers, daylilies, hostas, hydrangeas, kale, lettuce, peas, radishes, roses, saffron, snapdragons, spinach, swiss chard, turnips
September
Plant for fall: azaleas, bearded irises, cabbages, cauliflower, clematis, coneflowers, crocuses, daffodils, daylilies, grass seed, hostas, hyacinths, hydrangeas, kale, lilies, ornamental alliums, peonies, radishes, roses, saffron, spinach, tulips
October
Plant for fall: crocuses, daffodils, garlic, hyacinths, lilies, ornamental alliums, peonies, tulips
Frost dates and zones by ZIP code in Caldwell
Caldwell's 3 main ZIP codes take their frost dates from 3 different NOAA stations: the typical last frost ranges from April 23 in 83607 to April 29 in 83605. Every one of them is in zone 7a.
Planting dates for popular crops in Caldwell
| Plant | Start indoors | Plant or sow outdoors | Fall planting |
|---|---|---|---|
| Tomatoes | Mar 24 to Apr 7 | May 19 to Jun 2 | — |
| Strawberries | — | Mar 18 to Apr 1 | — |
| Lettuce | Mar 4 to 18 | Apr 22 to May 6 | Jul 14 to Aug 18 |
| Cilantro | Mar 18 to Apr 1 | Apr 29 to May 6 | — |
| Basil | Mar 31 to Apr 14 | May 19 to 26 | — |
| Potatoes | — | Apr 16 to 23 | — |
| Garlic | — | Mar 18 to Apr 1 | Oct 13 to 27 |
| Onions | Jan 7 to Feb 18 | Apr 1 to 15 | — |
| Cucumbers | Apr 21 to May 5 | May 19 to Jun 2 | — |
| Pumpkins | Apr 21 to May 5 | May 19 to Jun 2 | — |
| Peppers | Mar 3 to 31 | May 19 to Jun 2 | — |
| Carrots | — | Apr 8 to 29 | Jul 21 to Aug 11 |
| Sweet Potatoes | — | Jun 9 to 16 | — |
| Watermelons | Apr 14 to 28 | May 19 to Jun 2 | — |
| Sweet Corn | — | Apr 29 to May 13 | — |
| Green Beans | — | May 19 to Jun 2 | — |
| Zucchini | Apr 21 to May 5 | May 19 to Jun 2 | — |
| Broccoli | Feb 11 to Mar 4 | Apr 1 to 15 | Jul 28 to Aug 25 |
| Peas | — | Mar 18 to Apr 1 | Jul 21 to Aug 4 |
| Spinach | Mar 18 to 25 | Apr 22 to May 6 | Aug 4 to Sep 8 |
| Sunflowers | — | Apr 29 to May 20 | — |
| Zinnias | May 30 to Jun 6 | Jun 27 to Jul 11 | — |
| Tulips | — | — | Sep 1 to Oct 27 |
| Daffodils | — | — | Sep 1 to Oct 13 |
| Grass Seed | — | Mar 18 to Apr 1 | Sep 1 to 15 |
Nearby cities
- Nampa, ID zone 7a, last frost Apr 24
- Meridian, ID zone 7a, last frost Apr 24
- Boise City, ID zone 6b, last frost Apr 24
- Twin Falls, ID zone 6b, last frost May 9
- Pocatello, ID zone 6a, last frost May 16
- Kennewick, WA zone 7b, last frost Mar 28
Planting in IdahoAbout zone 7aPrintable calendar for Caldwell
Questions
When is the last frost in Caldwell?
Around April 29 in a typical year, based on NOAA's 1991-2020 records for Nampa Sugar Factory. There is still a 1 in 10 chance of frost after May 18.
What planting zone is Caldwell in?
USDA hardiness zone 7a (2023 map). The zone tells you which perennials survive the winter; planting dates depend on frost dates instead.
When should I plant tomatoes in Caldwell?
Start seeds indoors March 24 to April 7 and set plants out May 19 to June 2.
When is the first frost in Caldwell?
Around October 13 in a typical year, and before September 29 about 1 year in 10.