When should I plant watermelon in ZIP 85701?

In ZIP 85701, the main watermelon target is around Mar 1, based on the representative Tucson frost station and USDA zone 9b.

When should I start watermelon seeds indoors in 85701?

Start watermelon seeds indoors in ZIP 85701 around Jan 25, about 21 days before the Feb 15 last-frost estimate.

Is this a guaranteed planting date?

No. GrowZone uses frost-date estimates, hardiness zones, and crop timing rules for planning. Local microclimates and current weather can shift the right date.

ZIP 85701 planting calendar

When to plant watermelon in Tucson, AZ - Zone 9b

Q: When is the first frost in Tucson?

Tucson (ZIP 85701) has an average first fall frost around Dec 5, leaving about 293 frost-free days.

In ZIP 85701, plant watermelon around Mar 1; this uses the Tucson frost station, USDA zone 9b, and watermelon timing rules.

Your Tucson calendar has a 293-day estimated frost-free season. This estimate uses the representative Tucson frost station, USDA zone 9b, and watermelon timing rules.

Source: tucson-intl frost station, USDA zone 9b, 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 tucson-intl frost station and USDA zone 9b, last updated 2026-06-28.

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

USDA zone 9b Tucson frost station University of Arizona Extension Updated 2026-06-28

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Answer first

When to start watermelon seeds indoors in Tucson

In ZIP 85701, start watermelon seeds indoors around Jan 25, about 21 days before the Feb 15 last-frost estimate.

Start watermelon seeds indoors in Tucson around Jan 25, about 21 days before the Feb 15 last-frost estimate.

Seed starting schedule

Watermelon dates for Tucson, AZ

Step	Date	How to use it
Start Indoors	January 25, 2026	Start seeds under lights or in a bright indoor seed-starting space.
Transplant Outdoors	March 1, 2026	Move hardened-off seedlings outside after the frost-risk window.
Direct Sow	March 1, 2026	Sow seed outside when the crop and soil can handle the window.

Last frost

When is the last frost in Tucson?

Tucson (ZIP 85701) has an average last spring frost around Feb 15.

First frost

When is the first frost in Tucson?

The average first fall frost is around Dec 5, giving about 293 frost-free days.

Season map

Watermelon windows by month

JanFebMarAprMayJunJulAugSepOctNovDec

Start indoors

Jan 25

Direct sow

Mar 1

Transplant

Mar 1

Harvest

May 30

Frost watch

Sep 6

Reminder workflow

Every date has a next action

Start watermelon indoorsJan 25

Last frost windowFeb 15

Direct sow watermelonMar 1

Transplant watermelonMar 1

First watermelon harvest windowMay 30

Last watermelon sowing targetSep 6

Signal	Value	Why it matters
Last frost estimate	February 15, 2026	Warm-season transplant risk starts falling after this window.
First frost estimate	December 5, 2026	Fall planting counts backward from this date.
Season length	293 days	Longer seasons can support succession crops.
Spacing	36-60 in	Airflow and root space affect yield.
Soil temperature	70 F+	Seeds and transplants stall in cold soil.

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Local data

Why this date changes by ZIP

Tucson frost history and USDA zone 9b shift the safe planting window. GrowZone uses a local representative station instead of one national rule.

University of Arizona 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 Dec 5. A conservative last sowing target is around Sep 6.