Mullan, ID Frost Dates & Growing Season

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

Last spring frost
May 12
~50% chance of frost after
First fall frost
Sep 30
~50% chance of frost before
Growing season
141 days
frost-free stretch
USDA zone
≈ 6b
estimated from nearby reference
Risky (1 year in 10)MedianSafe (9 years in 10)
Last spring frost Apr 26 May 12 Jun 19
First fall frost Oct 17 Sep 30 Sep 12
Hard freeze (28°F), median last Apr 24 · first Oct 14

Computed from NOAA 1991–2020 climate normals at the MULLAN 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 Mullan

Computed from Mullan's own frost dates. Click any crop for the full zone-6 growing guide — varieties, spacing, fall plantings, and more.

CropStart seeds indoorsTransplantDirect sow
🍅 Tomatoes Mar 17 – Mar 31 May 19 – May 26
🫑 Peppers Mar 3 – Mar 17 May 26 – Jun 2
🥬 Lettuce Mar 31 – Apr 14 Apr 14 – Apr 28 Apr 14 – May 12
🫛 Peas Mar 31 – Apr 14
🥕 Carrots Apr 21 – May 12
🥦 Broccoli Mar 24 – Apr 7 Apr 21 – May 5
🥬 Kale Mar 31 – Apr 14 Apr 14 – Apr 28 Apr 14 – Apr 28
🥒 Cucumbers Apr 14 – Apr 21 May 19 – May 26 May 19 – May 26
🥒 Zucchini Apr 14 – Apr 21 May 19 – May 26 May 19 – May 26
🫘 Green Beans (Bush) May 19 – May 26
🌽 Sweet Corn May 19 – May 26
🌿 Basil Mar 31 – Apr 14 May 19 – May 26 May 26 – Jun 2
🧄 Garlic Fall: Aug 19 – Sep 16

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 Mullan's dates automatically after a lookup.

Reading the season in Mullan

At about 141 frost-free days, Mullan rewards efficiency: start warm-season crops indoors, favor short-season varieties, and lean on cold-tolerant crops — peas, kale, roots — that shrug off the shoulder-season frosts on either end.

Frequently asked questions

When is the last frost in Mullan, ID?

The average last spring frost in Mullan is around May 12, 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 Mullan, ID?

The average first fall frost in Mullan arrives around Sep 30. 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 Mullan?

About 141 frost-free days on average, from May 12 to Sep 30. That favors short-season varieties and transplants for warm-season crops, with cool-season vegetables doing the heavy lifting in spring and fall.

What USDA zone is Mullan in?

USDA zone 6b 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.