Frost Dates for Spencer, IA 51301

Last spring frost April 30 · First fall frost September 29 · 152 frost-free days · USDA Zone 5a

Frost probability for 51301

Frost10%50%90%
Spring (last frost)May 13April 30April 17
Fall (first frost)September 17September 29October 11

Dates come from NOAA 1971–2000 freeze probabilities at the nearest reporting station (25.7 km away); the 50% date is the median year.

Month by month in Spencer

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 30). 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 30. 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.
AugustFirst fall frost approaching (around September 29). Transplant fall brassicas. Sow spinach, arugula, and radishes.
SeptemberFirst frost around September 29. 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 152-day season

Frequently Asked Questions

What is the last frost date for Spencer, IA (ZIP 51301)?

The median last spring frost date for Spencer, IA (ZIP code 51301) is around April 30. 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 Spencer, IA?

The median first fall frost date for Spencer, IA is around September 29. 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 Spencer, IA?

The frost-free growing season in Spencer is about 152 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 Spencer, IA?

Based on frost date patterns, Spencer 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 Spencer, IA?

Start tomato seeds indoors 6–8 weeks before your last frost date (around April 30). For Spencer, that's roughly March 5 to March 19. Transplant outdoors 1–2 weeks after your last frost.

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