GrowZone

Seed-start answer

Start tomatoes seeds indoors around Mar 24

In ZIP 80012, start tomatoes seeds indoors around Mar 24, about 42 days before the May 5 last-frost estimate.

Source: denver-intl 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.

This uses ZIP 80012, the Denver frost station, and the May 5 last-frost estimate.

Seed starting schedule

Tomatoes dates for Aurora, CO

StepDateHow to use it
Start IndoorsMarch 24, 2026Start seeds under lights or in a bright indoor seed-starting space.
Transplant OutdoorsMay 12, 2026Move hardened-off seedlings outside after the frost-risk window.