How the answer is decided

Plant Yet? answers one question for every incorporated town in Colorado, once a day: should I plant, wait, or cover tonight? It is guidance only — not a guarantee about your garden.

Guidance only

Frost dates are 30-year averages from a weather station that may be miles from your yard. Forecasts change during the day and we fetch them once, early in the morning. Cold air pools in low spots, and a sheltered south wall can be a week ahead of an open field. Use the answer as a starting point, look at the numbers under it, and check the National Weather Service forecast before a cold night.

The four answers

Plant: Today is inside the crop's planting window for your town, and the coldest of the next 7 nights stays above the crop's cold limit.
Wait: Anything else in spring (from March 1). We always say why: “typical last frost here is May 12” or “28°F forecast Thursday night”.
Cover tonight: Tonight's forecast low is at or below the crop's cold-damage temperature, during the weeks that crop is normally in the ground. This outranks Plant and Wait.
Off-season: “Start seeds indoors on [date]” or “Next planting window opens [date]”.

The big answer at the top of a town page is the most urgent one among its crops: Cover tonight first, then Plant, then Wait, then off-season.

The details

Typical last and first frost are the dates with a 50% chance of a later (spring) or earlier (fall) 32°F night at the town's matched station.
Planting window opens the sourced number of weeks before or after typical last frost — for example CSU's “2–4 weeks before” for hardy crops opens 4 weeks before.
Planting window closes on the last day a planting could still mature before typical first fall frost (first frost minus the crop's sourced days to harvest), or at the end of the sourced range if that is later. For basil, chives and cilantro no source gives days to harvest or a last planting date, so we don't invent one: the window runs to the typical first fall frost.
Cold limit for Plant. Where an extension source states a minimum night temperature for planting out (eggplant, pepper, tomato and basil), we use it. For every other crop no such number is published, so the check is the crop's sourced cold-damage temperature instead. Potato, chives, cilantro and dill have neither, so they show their dates but never a Plant answer.
In the ground means from the day the window opens until the date by which 9 falls in 10 have had a freeze. Outside those weeks there is no Cover tonight.
Seed-starting dates count back from typical last frost, or from the day the window opens when the source says “weeks before transplanting”.
Tonight is the first night period in the forecast; the 7-night low is the coldest night period of the 7 we store.

Stale forecasts

If a town's forecast can't be fetched, we keep its last good one and show the time it was fetched. Once a forecast is more than 36 hours old the page shows Forecast unavailable instead of an answer — a stale Plant or Cover is never shown as current. The page checks this in your browser too, so it holds even if our daily update stops.

No nearby frost record

Each town uses the nearest NOAA station that has complete freeze data, is within 25 miles, and is within 500 feet of the town's elevation. If no station qualifies, the town shows “No nearby frost record” and gets no planting dates — we never borrow a far-away or much lower station. Today that is 20 of 273 towns, mostly in the mountains.

Data sources

Towns and coordinates: Every incorporated Colorado city and town (273) from the U.S. Census Bureau 2025 Gazetteer Files — Places, Colorado, fetched Nov 11, 2026. The location is the Census “internal point” of the town.
Elevation: USGS Elevation Point Query Service at that point. Each town page links its own query.
Frost history: NOAA NCEI 1991–2020 U.S. Climate Normals, annual/seasonal station files: probability of the last spring and first fall 32°F minimum at 10%, 50% and 90% (documentation). Fetched Nov 11, 2026.
Forecast: National Weather Service API (api.weather.gov) 7-day forecast for each town's grid cell, fetched once a day around 4:30 am Denver time. Every town page shows its fetch time.
Crops: 31 vegetables and herbs. Every value links to the university extension page it comes from (Colorado State University Extension first, then other land-grant universities), last checked Nov 11, 2026. Values we couldn't source are left out, not estimated.

What this site doesn't do

No accounts, no ads, no tracking scripts, no cookies, and no AI at runtime: the pages are plain files rebuilt once a day from public data. The code and all the data are in a public repository.