Arrowrock Dam, ID Frost Dates & Growing Season

The two dates every Arrowrock Dam garden is planned around, plus ready-computed planting windows for the most popular crops.

Last spring frost
Apr 28
~50% chance of frost after
First fall frost
Oct 14
~50% chance of frost before
Growing season
169 days
frost-free stretch
USDA zone
≈ 7a
estimated from nearby reference
Risky (1 year in 10)MedianSafe (9 years in 10)
Last spring frost Apr 11 Apr 28 May 16
First fall frost Oct 29 Oct 14 Oct 1
Hard freeze (28°F), median last Apr 6 · first Oct 27

Computed from NOAA 1991–2020 climate normals at the ARROWROCK DAM station. "Safe" means frost past that date happens only about one year in ten. Your exact garden can still run days either way with elevation and terrain — check your own ZIP with the frost date lookup.

Planting windows for Arrowrock Dam

Computed from Arrowrock Dam's own frost dates. Click any crop for the full zone-7 growing guide — varieties, spacing, fall plantings, and more.

CropStart seeds indoorsTransplantDirect sow
🍅 Tomatoes Mar 3 – Mar 17 May 5 – May 12
🫑 Peppers Feb 17 – Mar 3 May 12 – May 19
🥬 Lettuce Mar 17 – Mar 31 Mar 31 – Apr 14 Mar 31 – Apr 28
🫛 Peas Mar 17 – Mar 31
🥕 Carrots Apr 7 – Apr 28
🥦 Broccoli Mar 10 – Mar 24 Apr 7 – Apr 21
🥬 Kale Mar 17 – Mar 31 Mar 31 – Apr 14 Mar 31 – Apr 14
🥒 Cucumbers Mar 31 – Apr 7 May 5 – May 12 May 5 – May 12
🥒 Zucchini Mar 31 – Apr 7 May 5 – May 12 May 5 – May 12
🫘 Green Beans (Bush) May 5 – May 12
🌽 Sweet Corn May 5 – May 12
🌿 Basil Mar 17 – Mar 31 May 5 – May 12 May 12 – May 19
🧄 Garlic Fall: Sep 2 – Sep 30

Want this for all 50 crops, or as a printable seed-shelf schedule? Use the planting calendar and the seed starting scheduler — both can use Arrowrock Dam's dates automatically after a lookup.

Reading the season in Arrowrock Dam

Roughly 169 frost-free days gives Arrowrock Dam gardeners room for nearly every common vegetable. Warm-season crops go out after Apr 28; a fall garden sown in late summer matures comfortably before the Oct 14 frost.

Frequently asked questions

When is the last frost in Arrowrock Dam, ID?

The average last spring frost in Arrowrock Dam is around Apr 28, based on 1991–2020 climate normals. That's a median — about half of years see a later frost, so tender crops are safest going out a week or two after this date.

When is the first frost in Arrowrock Dam, ID?

The average first fall frost in Arrowrock Dam arrives around Oct 14. Crops still in the garden need to mature before then, and frost-tender plants need harvesting or protection as the date approaches.

How long is the growing season in Arrowrock Dam?

About 169 frost-free days on average, from Apr 28 to Oct 14. That fits nearly all common vegetables, though the longest-season melons and sweet potatoes benefit from transplants.

What USDA zone is Arrowrock Dam in?

USDA zone 7a on the 2023 Plant Hardiness Zone Map. Note that zones describe winter cold, not frost timing — these frost dates are the numbers to plan plantings around.