Frost Dates for Sioux City, IA 51106

Last spring frost April 29 · First fall frost October 2 · 156 frost-free days · USDA Zone 5a

Frost probability for 51106

Frost10%50%90%
Spring (last frost)May 13April 29April 15
Fall (first frost)September 19October 2October 15

Dates come from NOAA 1971–2000 freeze probabilities at the nearest reporting station (38.2 km away); the 50% date is the median year.

Frost dates by ZIP code in Sioux City, IA

ZIPLast spring frost (50%)First fall frost (50%)Zone
51106April 29October 25a
51104April 29October 25a
51103April 29October 25a
51105April 29October 25a
51108April 29October 25a
51109April 29October 25a
51101April 29October 25a
51111April 28October 35a

Month by month in Sioux City

MonthWhat to do
JanuaryPlan your garden layout and order seeds. Research varieties suited to your frost dates.
FebruaryStart peppers and eggplant indoors 8–10 weeks before your last frost (around April 29). Start tomatoes about two weeks later, 6–8 weeks before last frost.
MarchStart herbs, basil, and squash indoors (4–6 weeks before frost). Direct sow peas, spinach, and lettuce if soil is workable.
AprilLast frost around April 29. Transplant cold-hardy crops (broccoli, kale, cabbage). Harden off tomato and pepper seedlings.
MayFrost has passed. Transplant tomatoes, peppers, and basil outdoors. Direct sow beans, cucumbers, squash, and zucchini.
JuneSuccession plant lettuce and greens. Keep beds weeded and watered consistently.
JulyHarvest regularly to encourage production. Monitor for pests and disease.
AugustMidsummer: harvest beans, zucchini, cucumbers. Start brassica seeds indoors for fall.
SeptemberFirst fall frost approaching (around October 2). Transplant fall brassicas. Sow spinach, arugula, and radishes.
OctoberFirst frost around October 2. Harvest tomatoes and peppers before frost. Cover cold-hardy crops with row covers to extend the season.
NovemberHarvest remaining cold-hardy crops: kale, carrots, and beets. Plant garlic bulbs for next year.
DecemberClean up spent plants. Add compost to beds. Rest, review, and plan next year's garden.

What grows in a 156-day season

Frequently Asked Questions

What is the last frost date for Sioux City, IA (ZIP 51106)?

The median last spring frost date for Sioux City, IA (ZIP code 51106) is around April 29. 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 Sioux City, IA?

The median first fall frost date for Sioux City, IA is around October 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 Sioux City, IA?

The frost-free growing season in Sioux City is about 156 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 Sioux City, IA?

Based on frost date patterns, Sioux City 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 Sioux City, IA?

Start tomato seeds indoors 6–8 weeks before your last frost date (around April 29). For Sioux City, that's roughly March 4 to March 18. Transplant outdoors 1–2 weeks after your last frost.

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