Frost-Free Growing Seasons in San Miguel Basin & Surrounding Areas
Microclimates in the mountains can vary greatly, which means that frost-free growing seasons differ depending on location. Areas at higher elevations or on slopes tend to be warmer as they absorb more heat from the sun and allow cold air to drain, while low-lying areas may experience colder temperatures where frost can settle.
Average Frost-Free Growing Seasons by Community
Based on the average (50% chance) last frost above 32.5°F in the spring and first frost below 32.5°F in the fall.
| Community | Frost-Free Dates | Comments |
|---|---|---|
| Norwood | June 9 – September 21 (104 days) | Latest data shows a shorter growing season by about 1 week. |
| Redvale | June – September/October | Slightly longer season than Norwood due to warmer daytime temps. |
| Nucla | June – September/October | Cooler than Naturita, but has a longer season than Norwood. |
| Naturita | June – September/October | Longer season than Norwood. |
| Paradox East | May 14 – September 24 (133 days) | One of the longest growing seasons in the area. |
| Paradox West | May 8 – October 5 (150 days) | The longest frost-free season in the area! |
| Telluride | June 28 – August 31 (64 days) | Some locals plant by June 15th for the last frost. |
| Placerville | July 19 – August 15 (27 days) | Short growing season, labeled as the ‘banana belt,’ but data is questionable. |
| Mountain Village/Ophir | No official data | Local input is valued to understand the microclimate. |
| Uravan | May 2 – October 13 (164 days) | Longest growing season in the area, despite no town. |
| Rico | July 1 – August 31 (61 days) | Short growing season, influenced by altitude. |
| Ridgway | June 21 – September 8 (79 days) | Can experience hard freezes even in summer. |
| Ouray | May 29 – September 26 (120 days) | Locals traditionally plant on Memorial Day weekend. |
| Silverton | July 12 – August 15 (34 days) | Significant increase in frost-free days from previous data. |
Data from over 50 years of weather station records (1948-2005).
Hardiness of Annual Flowers
Understanding flower hardiness is key to knowing when to plant outdoors. Here are the general guidelines for annual flowers based on their tolerance to cold.
| Type of Flower | Hardiness | Planting Timing |
|---|---|---|
| Hardy Annuals | Tolerate cold soils and light frosts | Plant out 4 weeks before the average last spring frost date |
| Examples: Pansies, Snapdragons, Calendula, Sweet Alyssum | ||
| Half-Hardy Annuals | Tolerate cool soils but not frosts | Plant 2 weeks before last spring frost |
| Examples: Geraniums, Petunias, Lobelia, Gazanias | ||
| Tender Annuals | Need warm soil and do not tolerate frost | Plant 1+ weeks after the last frost |
| Examples: Zinnias, Salvia, Coleus, Begonias |
Note: Cool-season annuals may decline in summer heat.
Hardiness of Vegetable Crops
Vegetables also have varying tolerances to cold temperatures. Here’s a quick guide:
| Type of Vegetable | Hardiness | Examples |
|---|---|---|
| Cool-Season Hardy Vegetables | Can tolerate 24-28°F | Arugula, Kale, Spinach, Broccoli, Brussels Sprouts, Garlic |
| Cool-Season Semi-Hardy Vegetables | Can tolerate 28-32°F | Beets, Carrots, Lettuce, Radishes, Peas |
| Warm-Season Vegetables (Frost-sensitive) | Cannot tolerate <32°F | Beans, Corn, Peppers, Tomatoes, Melons, Pumpkins |
| Warm-Season Vegetables (Heat-sensitive) | Best grown in temperatures >50°F | Sweet Potatoes, Basil |
Note: Some warm-season vegetables may withstand light frosts if followed by warm day temperatures.
More Information & Resources
This sheet was compiled by Yvette Henson, former Extension Director and Agriculture, Natural Resources, and Horticulture Agent for the San Miguel Basin. For more details on growing in high-altitude, low-water conditions or other gardening topics, visit us at:
- Office: 1120 Summit Street, Norwood, CO 81423 (Across from the Fairgrounds)
- Phone: 970-327-4393
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Colorado State University Extension is an equal opportunity provider. For more information, visit:
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Gardening in the San Miguel Basin can be challenging due to the area’s unique climate, but with the right knowledge, it’s possible to grow a wide variety of crops and flowers. We’re here to help! 🌱
