Ontario, California planting calendar and frost dates

Frost dates in Ontario

A 32°F night is rare here: it happens in about 41% of years, so median frost dates do not describe a typical year.

NOAA U.S. Climate Normals 1991-2020 for Ontario International Airport, 2.9 miles E 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 Ontario

Cool-season crops are planted from late summer through winter, but the window is shorter than on the coast because summers are too hot for lettuce, peas and cole crops and occasional winter frosts can nip tender growth. Warm-season crops go in from April, after frost danger, through June; hot, dry summers ripen tomatoes, melons and peppers well but heat above the mid-90s can stop fruit set in July and August. Rain comes almost entirely November to March. The months below follow the planting calendar for Southern California Inland Valleys from the Cooperative Extension sources listed.

1. January

   Plant: asparagus, azaleas, beets, blackberries, broccoli, cabbages, carrots, cauliflower, daffodils, grapes, green onions, hyacinths, kale, lettuce, onions, parsley, peas, radishes, raspberries, rhubarb, roses, spinach, strawberries, sweet peas, swiss chard, tulips, turnips, wildflowers

2. February

   Plant: asparagus, azaleas, beets, blackberries, broccoli, cabbages, carrots, cauliflower, chives, cilantro, dill, gladioli, grapes, green onions, kale, lavenders, lettuce, onions, parsley, peas, potatoes, radishes, raspberries, rhubarb, roses, spinach, strawberries, swiss chard, turnips, wildflowers

3. March

   Plant: avocados, beets, blackberries, carrots, chives, cilantro, dahlias, dill, gladioli, grapes, green onions, kale, lavenders, lettuce, mints, oregano, parsley, peas, potatoes, radishes, raspberries, rhubarb, rosemary, sage, spinach, strawberries, swiss chard, thyme, turnips

4. April

   Plant: avocados, basil, beets, cantaloupes, chives, cilantro, cosmos, cucumbers, dahlias, dill, eggplants, gladioli, green beans, green onions, kale, lavenders, marigolds, mints, okra, oregano, parsley, peppers, potatoes, pumpkins, rosemary, sage, strawberries, sunflowers, sweet corn, swiss chard, thyme, tomatoes, turnips, watermelons, winter squash, zinnias, zucchini

5. May

   Plant: avocados, basil, cantaloupes, chives, cilantro, cosmos, cucumbers, dahlias, eggplants, gladioli, green beans, marigolds, okra, parsley, peppers, pumpkins, rosemary, sunflowers, sweet corn, sweet potatoes, tomatoes, watermelons, winter squash, zinnias, zucchini

6. June

   Plant: avocados, cantaloupes, cosmos, cucumbers, dahlias, eggplants, gladioli, green beans, marigolds, okra, peppers, pumpkins, sunflowers, sweet corn, sweet potatoes, tomatoes, watermelons, winter squash, zinnias, zucchini

7. July

   Plant: cosmos, cucumbers, green beans, marigolds, sunflowers, sweet corn, zinnias, zucchini

8. August

   Plant: broccoli, cabbages, cauliflower, green beans, potatoes

9. September

   Plant: beets, broccoli, cabbages, carrots, cauliflower, chives, cilantro, green onions, kale, lettuce, parsley, poppies, potatoes, radishes, snapdragons, spinach, sweet peas, swiss chard, turnips

10. October

    Plant: asparagus, azaleas, beets, broccoli, cabbages, carrots, cauliflower, chives, crocuses, daffodils, garlic, green onions, hyacinths, kale, lettuce, onions, parsley, poppies, radishes, sage, snapdragons, spinach, strawberries, sweet peas, swiss chard, thyme, tulips, turnips, wildflowers

11. November

    Plant: asparagus, azaleas, beets, broccoli, cabbages, carrots, cauliflower, cilantro, crocuses, daffodils, garlic, green onions, hyacinths, kale, lettuce, onions, parsley, poppies, radishes, snapdragons, spinach, strawberries, sweet peas, swiss chard, tulips, turnips, wildflowers

12. December

    Plant: asparagus, azaleas, beets, broccoli, cabbages, carrots, cauliflower, daffodils, green onions, hyacinths, kale, lettuce, onions, parsley, radishes, spinach, strawberries, sweet peas, swiss chard, tulips, turnips, wildflowers

Frost dates and zones by ZIP code in Ontario

All 3 of Ontario's main ZIP codes take their frost dates from Ontario International Airport, so the dates on this page apply across the city. Every one of them is in zone 10a.

Ontario International Airport also supplies the frost dates for Rancho Cucamonga, Chino and Upland, so their planting calendars match Ontario's.

Nearby cities

• Eastvale, CA zone 10a, last frost Jan 17
• Chino, CA zone 10a
• Upland, CA zone 10a
• Rancho Cucamonga, CA zone 10a
• Jurupa Valley, CA zone 10a, last frost Jan 9
• Pomona, CA zone 10a, last frost Jan 8