PlantingWindowPlan / no guesswork hidden

PlantingWindowPlan: frost-safe planting date calculator

Turn your entered forecast and crop thresholds into a short, explainable planting window. See exactly which conditions trigger a delay or protection task.

No sign-inLocal calculationsEditable assumptionsSource-linked methodology

Set the crop thresholds

Before you calculateFollow the evidence trail
  1. 01
    CropName the crop and start date
  2. 02
    ForecastSet pass/fail thresholds
  3. 03
    RecheckReview dated weather rows

Illustrative starting inputs. Replace them with your own measurements and evidence.

01 / Set your assumptions

Set the crop thresholds

Enter the crop, soil, air, wind, and rain limits first. The result becomes a dated journal entry that explains why a day passes or waits.

Job stateSet, then recheckSwitch from threshold inputs to the dated forecast task list without clearing your crop plan.
01Crop and datesStart with the crop, plan date, and forecast issue date.
Thresholds below are editable planning inputs, not a universal planting rule.
Used only if this crop is started indoors before transplanting.
Days between repeat sowings after the candidate day.
How many repeat sowings to schedule after the candidate day.
02Weather thresholdsSet soil, air, wind, and rain limits you will actually honor.

Live forecast for the planting window

Saved data · as of 2026-09-11

Uses the shared MET Norway weather feed for daily lows, highs and rain, plus Open-Meteo’s free, keyless geocoding to search a location. Nothing is requested until you pick a location below, and the forecast table stays editable after it loads.

Look up a USDA hardiness zone (optional)

Uses the free, keyless phzmapi.org ZIP lookup. Nothing is requested until you click Look up zone. The result is reference information only, not a live forecast or a planting-date input.

3 records

Daily forecast snapshot

These are illustrative weather inputs, not a live forecast. Replace them with a current, appropriately licensed forecast for your location.

Edit records Review every assumption
Forecast dayLow °FHigh °FWind mphRain inchesForecast sourceRemove
Seasonal journal

A calendar that explains its changes.

The dated task list shows the candidate day and each trigger so a recheck has a clear reason.

Computed locally
First candidate window: 2026-09-12

The entered air, rain, wind, and soil thresholds pass on this day. Recheck soil and the latest forecast before planting.

Season timeline

Season timelineIndoor seed start: 2026-08-01 (day 0)Indoor seed start2026-08-01Candidate sow day: 2026-09-12 (day 42)Candidate sow day2026-09-12Succession sowing 1: 2026-09-26 (day 56)Succession sowing 12026-09-26Succession sowing 2: 2026-10-10 (day 70)Succession sowing 22026-10-10Succession sowing 3: 2026-10-24 (day 84)Succession sowing 32026-10-24Illustrative harvest: 2026-11-26 (day 117)Illustrative harvest2026-11-26
Timeline dates table
Season timeline
StageDateOffset
Indoor seed start2026-08-01Day 0
Candidate sow day2026-09-12Day 42
Succession sowing 12026-09-26Day 56
Succession sowing 22026-10-10Day 70
Succession sowing 32026-10-24Day 84
Illustrative harvest2026-11-26Day 117

Forecast-adjusted task list

2026-09-1148 / 72 °F8 mph0 inDelay / reviewOvernight temperature below crop threshold
2026-09-1255 / 76 °F6 mph0.1 inCandidate planting dayEntered thresholds pass
2026-09-1356 / 78 °F7 mph0 inCandidate planting dayEntered thresholds pass

Season calendar

Indoor seed start2026-08-016 weeks before the candidate day; skip if direct-sowing
Candidate sow day2026-09-12First day passing every entered threshold
Succession sowing 12026-09-26+14 days from the candidate day
Succession sowing 22026-10-10+28 days from the candidate day
Succession sowing 32026-10-24+42 days from the candidate day
Illustrative harvest2026-11-2675 days after the candidate day; not a forecast

Companion planting reference

Commonly grown nearBasil, Marigold, Carrot, Onion
Commonly kept apartBrassicas (cabbage, broccoli, kale), Fennel, Corn
Candidate planting day2026-09-12Only within the imported forecast
Frost-review nights0Forecast low at or below 32°F
Forecast snapshot age0 daysMore than two days triggers a refresh warning
Illustrative harvest date2026-11-2675 days after the candidate day; not a forecast
Indoor seed-start date2026-08-016 weeks before the candidate day; only if started indoors
Next succession sowing2026-09-263 more at 14-day intervals

Before you act

  • 0 gaps between forecast days. Missing days are not assumed safe.
  • Soil temperature is a user measurement, not a modeled future forecast. Microclimates, variety, hardening-off, containers, and planting method can change the decision.
  • Calendar exports are static reminders. No background weather monitoring or automatic notifications are active.
  • Companion-planting associations are general guidance to verify locally, not a substitute for crop rotation or pest planning.
Calculation notes & limitations

A day is a candidate only if every entered air, wind, rain, and soil condition passes and the forecast is no more than two days old.

Harvest dates simply add the user-entered maturity days. Weather, day length, variety, and whether days are counted from sowing or transplanting can materially change harvest timing.

Succession sowing dates repeat the entered interval after the candidate day; they do not re-check weather thresholds for those future dates.

The indoor seed-start date subtracts the entered weeks from the candidate day; it does not confirm the crop is normally started indoors.

Saving is optional. Files and records never leave your browser through this app.
Field note / forecast uncertainty

A planting date is a recheckable decision.

Worked example: September 12 candidate, November 26 illustration

With the starting inputs, September 12, 2026 passes the entered air, rain, wind, and soil thresholds. A 75-day maturity setting produces an illustrative November 26 harvest date. It is a planning calculation, not a forecast of harvest conditions.

Read a forecast as a snapshot

The National Weather Service explains that forecasts are produced from observations, models, and forecaster judgment; the probabilistic view communicates uncertainty. Keep the issue date and age visible, then refresh the forecast before acting.

Use extension guidance for the crop

University of Minnesota Extension’s vegetable-garden guidance is a primary growing reference for planting considerations. Adapt thresholds to the crop, local conditions, and your own soil measurement rather than treating a single pass as certainty.

Primary referencesNational Weather Service forecasts University of Minnesota Extension vegetable gardening
02 / Look under the hood

The method is part of the tool.

Keep current forecast records separate from climate normals. Enter the forecast issue date and the actual date represented by each row.

Compare each day with explicit, editable crop thresholds for overnight temperature, heat, wind, rainfall, and measured soil temperature.

Explain every delay, refuse to fill missing forecast days, and export static reminders that tell you to recheck conditions.

Read the full methodology
By zone / PlantingWindowPlan

When to plant, by USDA hardiness zone

Worked threshold examples for each crop across USDA zones 3-10, each linking a prefilled plan.

Browse planting zone guides
Field notes / PlantingWindowPlan

How PlantingWindowPlan calculates your result

Turn your entered forecast and crop thresholds into a short, explainable planting window. See exactly which conditions trigger a delay or protection task.

PlantingWindowPlan: a verification checklist

A useful result is one you can explain, reproduce, and challenge.