When is the last frost in Sioux City, IA?

The average last spring frost (50% probability of 32°F) in Sioux City is around April 29, based on NOAA/NCEI 1991–2020 normals at the Sioux City Ang, IA station (6.8 mi away). Half of years it falls outside that date, so wait 1–2 weeks past it before setting out frost-tender plants.

When is the first fall frost in Sioux City?

The average first fall frost in Sioux City, IA is around October 7, giving roughly a 161-day frost-free growing season.

What planting zone is Sioux City, IA?

Sioux City is in USDA plant hardiness zone 5a (average annual extreme minimum temperature -20 to -15°F), from the 2023 USDA Plant Hardiness Zone Map.

What is the weather like in Sioux City?

In Sioux City, IA the warmest month is July (avg high 85°F) and the coldest is January (avg low 10.4°F). It averages about 29.3″ of precipitation a year and 36″ of snow.

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Sioux City, IA Planting Calendar & Frost Dates

USDA hardiness zone 5a · ZIP 51101 · elevation 334′ · NOAA & USDA data

Sioux City is in USDA hardiness zone 5a (winters can dip to -20 to -15°F), with a growing season of about 161 days between the average last spring frost (April 29) and first fall frost (October 7). The warmest month is July (avg high 85°F); the coldest is January (avg low 10.4°F). It averages 29.3″ of precipitation a year and 36″ of snow, mostly mid-winter. Start cool-season crops several weeks before the last frost; wait until after it for tomatoes, peppers and other tender crops.

Hardiness zone

min temp -20 to -15°F

Last spring frost

April 29

avg (50% prob, 32°F)

First fall frost

October 7

avg (50% prob, 32°F)

Growing season

161 days

frost-free window

Warmest month

July

avg high 85°F

Month-by-month typical weather in Sioux City

Average conditions from the NOAA/NCEI 1991–2020 U.S. Climate Normals at Sioux City Gateway Ap, IA (7.1 mi away). Temperatures °F, precipitation & snow in inches.

Month	Avg high	Avg low	Mean	Precip (in)	Snow (in)
January	29.5	10.4	20	0.7	7.7
February	34.2	14.8	24.5	0.9	8.7
March	47.6	25.9	36.7	1.8	5.7
April	61.1	36.7	48.9	3.2	2.3
May	72.3	48.7	60.5	3.9	0
June	81.9	59.4	70.7	4.4	0
July	85	63.4	74.2	3.4	0
August	82.6	60.8	71.7	3.9	0
September	76.6	51.2	63.9	2.8	0
October	62.8	37.9	50.3	2.2	0.8
November	46.8	25	35.9	1.3	3.2
December	33.4	14.8	24.1	1	7.6

What to plant when in Sioux City

Crop	Season	What to do & when
Tomatoes	warm	Start seeds indoors: March 18 · Transplant out: May 6
Peppers	warm	Start seeds indoors: March 4 · Transplant out: May 13
Cucumbers	warm	Direct sow: May 6
Zucchini / squash	warm	Direct sow: May 6
Bush beans	warm	Direct sow: May 6
Sweet corn	warm	Direct sow: May 6
Basil	warm	Transplant out: May 6
Peas	cool	Sow (spring): March 25 · Sow (fall): August 12
Spinach	cool	Sow (spring): March 18 · Sow (fall): August 12
Lettuce	cool	Sow (spring): April 1 · Sow (fall): August 12
Kale	cool	Transplant (spring): April 8 · Sow (fall): July 29
Broccoli	cool	Transplant (spring): April 15
Carrots	cool	Sow (spring): April 8 · Sow (fall): July 29
Onions	cool	Transplant (spring): April 1
Potatoes	cool	Plant seed potatoes: April 15
Radishes	cool	Sow (spring): April 1 · Sow (fall): August 26

Dates are computed from Sioux City's average frost dates using standard cool-/warm-season timing. They're a starting point — a cold spring, a warm microclimate, or a fast-maturing variety can shift them by a week or two.

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Gear that helps you plant on time

Some links below are Amazon affiliate links (tag theboringthin-20). If you buy through them we may earn a small commission at no extra cost to you — it keeps this almanac free. We only list generic, genuinely-useful categories.

Soil thermometer →Know when the ground is warm enough to sow — the honest signal, not the calendar.Seed-starting trays + dome →Start tomatoes & peppers indoors on the schedule below.Seedling heat mat →Warms the soil for faster, more even germination indoors.Floating row cover / frost cloth →Buys you 4–8°F to beat an early or late frost.Raised garden bed kit →Warms and drains faster in spring than in-ground soil.Garden gloves →Basic kit for transplant day.

Nearby cities in Iowa

Council Bluffs, IA Ames, IA Urbandale, IA West Des Moines, IA Ankeny, IA Des Moines, IA Cedar Falls, IA Waterloo, IA

Sources & method. Hardiness zone: 2023 USDA Plant Hardiness Zone Map (PRISM Climate Group, Oregon State University). Frost dates & growing season: NOAA/NCEI 1991–2020 U.S. Climate Normals, nearest station with published freeze normals — Sioux City Ang, IA, 6.8 mi (confidence: high). Monthly weather normals: Sioux City Gateway Ap, IA, 7.1 mi (confidence: high). ZIP centroid from U.S. Census 2023 ZCTA data. Frost dates are the 50%-probability date — half of years frost occurs outside the stated date. Nothing here is invented; where the nearest station is far, we say so. Last updated 2026-07-22.