Frost Dates for Silverthorne, CO 80498

Last spring frost June 23 · First fall frost September 2 · 71 frost-free days · USDA Zone 5a

Frost probability for 80498

Frost10%50%90%
Spring (last frost)July 13June 23June 6
Fall (first frost)August 14September 2September 20

Dates come from NOAA 1971–2000 freeze probabilities at the nearest reporting station (33.3 km away); the 50% date is the median year.

Month by month in Silverthorne

MonthWhat to do
JanuaryPlan your garden layout and order seeds. Research varieties suited to your frost dates.
FebruaryStart the slowest-growing crops indoors: onions, leeks, and celery (10–12 weeks before last frost).
MarchOrganize planting supplies and seed-starting mix. Check stored garden tools.
AprilStart peppers and eggplant indoors 8–10 weeks before your last frost (around June 23). Start tomatoes about two weeks later, 6–8 weeks before last frost.
MayStart herbs, basil, and squash indoors (4–6 weeks before frost). Direct sow peas, spinach, and lettuce if soil is workable.
JuneLast frost around June 23. Transplant cold-hardy crops (broccoli, kale, cabbage). Harden off tomato and pepper seedlings.
JulyFrost has passed. Transplant tomatoes, peppers, and basil outdoors. Direct sow beans, cucumbers, squash, and zucchini.
AugustFirst fall frost approaching (around September 2). Transplant fall brassicas. Sow spinach, arugula, and radishes.
SeptemberFirst frost around September 2. Harvest tomatoes and peppers before frost. Cover cold-hardy crops with row covers to extend the season.
OctoberHarvest remaining cold-hardy crops: kale, carrots, and beets. Plant garlic bulbs for next year.
NovemberClean up spent plants. Add compost to beds. Rest, review, and plan next year's garden.
DecemberClean up spent plants. Add compost to beds. Rest, review, and plan next year's garden.

What grows in a 71-day season

Frequently Asked Questions

What is the last frost date for Silverthorne, CO (ZIP 80498)?

The median last spring frost date for Silverthorne, CO (ZIP code 80498) is around June 23. This is the 50th-percentile date — meaning half of all years see frost end before this date. Use the 10% and 90% dates to understand the full range of risk in your area.

What is the first fall frost date in Silverthorne, CO?

The median first fall frost date for Silverthorne, CO is around September 2. Plan to harvest or protect frost-sensitive crops like tomatoes and peppers at least a week before this date to avoid losses.

How long is the growing season in Silverthorne, CO?

The frost-free growing season in Silverthorne is about 71 days. This window — from your last spring frost to your first fall frost — is when warm-season vegetables thrive. Cold-hardy crops like kale, spinach, and peas can extend your season by weeks on either side.

What USDA hardiness zone is Silverthorne, CO?

Based on frost date patterns, Silverthorne falls approximately in 5a. USDA hardiness zones are determined by average annual minimum winter temperatures and guide both plant selection and planting timing for your location.

When should I start tomatoes indoors in Silverthorne, CO?

Start tomato seeds indoors 6–8 weeks before your last frost date (around June 23). For Silverthorne, that's roughly April 28 to May 12. Transplant outdoors 1–2 weeks after your last frost.

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