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ZIP 80903 planting calendar

When to plant watermelon in Colorado Springs, CO - Zone 6a

In ZIP 80903, plant watermelon around May 29; this uses the Colorado Springs frost station, USDA zone 6a, and watermelon timing rules.

Your Colorado Springs calendar has a 139-day estimated frost-free season. This estimate uses the representative Colorado Springs frost station, USDA zone 6a, and watermelon timing rules.

Source: colorado-springs-muni frost station, USDA zone 6a, last updated 2026-06-28. Verify locally before planting high-value crops because microclimates, current weather, and yard exposure can move the safe date.

Reviewed by GrowZone Editorial. Calculated from the colorado-springs-muni frost station and USDA zone 6a, last updated 2026-06-28.

In the Colorado Springs area, watermelon timing follows the Colorado Springs frost window, so the local ZIP date can differ from a broad zone-only calendar.

USDA zone 6a Colorado Springs frost station Colorado State University Extension Updated 2026-06-28
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Answer first

When to start watermelon seeds indoors in Colorado Springs

In ZIP 80903, start watermelon seeds indoors around Apr 24, about 21 days before the May 15 last-frost estimate.

Start watermelon seeds indoors in Colorado Springs around Apr 24, about 21 days before the May 15 last-frost estimate.

Seed starting schedule

Watermelon dates for Colorado Springs, CO

StepDateHow to use it
Start IndoorsApril 24, 2026Start seeds under lights or in a bright indoor seed-starting space.
Transplant OutdoorsMay 29, 2026Move hardened-off seedlings outside after the frost-risk window.
Direct SowMay 29, 2026Sow seed outside when the crop and soil can handle the window.

Last frost

When is the last frost in Colorado Springs?

Colorado Springs (ZIP 80903) has an average last spring frost around May 15.

First frost

When is the first frost in Colorado Springs?

The average first fall frost is around Oct 1, giving about 139 frost-free days.

Season map

Watermelon windows by month

JanFebMarAprMayJunJulAugSepOctNovDec
Start indoors
Apr 24
Direct sow
May 29
Transplant
May 29
Harvest
Aug 27
Frost watch
Jul 3

Reminder workflow

Every date has a next action

Start watermelon indoorsApr 24
Last frost windowMay 15
Direct sow watermelonMay 29
Transplant watermelonMay 29
Last watermelon sowing targetJul 3
First watermelon harvest windowAug 27
SignalValueWhy it matters
Last frost estimateMay 15, 2026Warm-season transplant risk starts falling after this window.
First frost estimateOctober 1, 2026Fall planting counts backward from this date.
Season length139 daysLonger seasons can support succession crops.
Spacing36-60 inAirflow and root space affect yield.
Soil temperature70 F+Seeds and transplants stall in cold soil.

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Local data

Why this date changes by ZIP

Colorado Springs frost history and USDA zone 6a shift the safe planting window. GrowZone uses a local representative station instead of one national rule.

Colorado State University Extension is the kind of local source to verify against when a crop is expensive, weather is unusual, or your yard has a cold pocket.

Crop note

Watermelon timing notes

Wait for warm soil; watermelon stalls when nights stay cool. Watermelon prefers full sun, 36-60 in spacing, and soil near 70 F+.

For fall, count backward from Oct 1. A conservative last sowing target is around Jul 3.