GardenTrack
Join the beta

Frost alerts

Partly live · The warning shows in the app. Getting it to a phone with the app closed needs push notifications, which are built and switched on. One person on our team has reported getting an alert on a real phone with the app fully shut, on 31 July 2026 — and a second, near-duplicate alert when they opened the app, which has since been fixed. That is one report, one phone, one occasion, and it is somebody here rather than a test we ran. Nobody has yet watched a push arrive on a device we control, so what we can honestly tell you is that it has worked once, not that it works reliably. Send yourself a test alert from the checklist on Today or from Profile — a minute now beats finding out on the night of a freeze.

Around six in the evening, your time, the app looks up tonight's forecast low for your garden and checks it against every plant you are growing. It warns you about the ones frost will end, and stays quiet about the hardy ones, because a light frost improves kale and warning you about that is how you learn to ignore the warning that matters.

What the warning tells you

The card names the temperature, names the plants at risk, and gives you the two things you can actually do about it: cover them, or pick what is on them. Tapping either records what you did.

It sits at the top of everything else on your Today screen, above even a hardening-off tray that is still outside. On the night it appears, it is the most important thing the app has to say.

Why hardy crops stay silent

This is the part people ask about, so it is worth being clear.

Every alert channel has a budget, and it is spent by the alerts that turn out not to matter. Warn somebody about their kale on a frosty night and they learn, correctly, that the warnings are noise. Then the night their tomatoes are at risk, they do not look.

So GardenTrack warns about tender plants and says nothing about hardy ones. Most fall nights, most gardens get nothing.

The temperature has to be about the right part of the plant

For about 40 crops we hold an exact number from a university source — the temperature at which that plant starts taking damage. A number on its own turns out to be almost useless, because it is always about one particular part of the plant at one particular time of year.

Apple is the clearest case. The figure is 28°F, and it is about open blossoms. In April that number is the most useful thing we know about your tree. In January the same tree is bare and does not care, and an alert every cold night all winter would just teach you to swipe it away — so that by April, when it finally means something, you are not reading it.

So every temperature we hold now says which part of the plant it is about: open flowers, new spring growth, a crop still sitting in the ground, or a shrub in the middle of winter. Your warning waits for the season it belongs to.

One more thing worth knowing. Some sources say “damaged at 28°F” and some say “fine down to 28°F” — opposite meanings, same number. We record which one it is and say it the way the source said it.

If you are hardening seedlings off

A tray sitting outside on a frost night is a different problem from a plant in the ground, and the app treats it as one. The frost warning appears above the hardening card, and the answer is almost always the same: bring them in early and skip the rest of today's step. A week of hardening off is recoverable. A frosted tray is not.

What it uses about your garden

Coordinates, to find your weather grid square. That is it. If you gave us an address when you set your frost dates, we used it to get a latitude and longitude and then discarded it — we have no use for your street and holding it because it was easy is not something we do.

Whose frost date the app is using

Every frost answer — how many days you have left, whether a crop will ripen in time, what is safe to plant now — is worked out from two dates: your average last spring frost and your average first autumn frost.

If you have told us where you garden, those are yours, from the weather record for your own location.

If you have not, the app uses roughly the middle of the country — a first frost around 21 October. It has to use something. Until 16 August 2026 it did not say which of the two you were looking at, so an average could read as a personal fact: in Denver that date is over a week out, and on the Gulf coast it is wrong by months.

Now anywhere the app is working from the average, it says so. Telling it where you garden takes a moment and changes every date on every screen at once.

Common questions

What time does the frost alert arrive?
**Around six in the evening, wherever you are — corrected 19 August 2026.** Late enough that tonight’s forecast has firmed up, early enough that you can still go out and do something about it. **It used to arrive at nine.** The alert went out at one fixed moment for the whole country, and that moment was six in the evening on the west coast and nine on the east. In September it is dark by then, so anyone east of the Rockies got a warning they could act on only with a torch — which is not a warning, it is a worry. Now it goes by the clock on your own phone. **One alert per night**, on the night it matters. **From 20 August 2026 that one-a-night limit is shared with the hot-spell alert**, and frost wins it. On a day forecast to freeze tonight and bake at the weekend, both are true and only this one is sent — the heat one waits on your Today screen instead. If your phone has never told us which time zone it is in, you will still get the old late-evening one until it does.
It says hot weather is coming. How hot, and how would I know it is right?
**From 19 August 2026 the card tells you the number.** It reads something like *"Around 99°F, and nights near 70°F"* rather than only *"Hot weather in 3 days"*. That was a fair complaint about a real gap: **the app has never shown you a temperature anywhere.** Weather decides when we warn you about heat, when a tray should come in, and whether it is worth planting this week — and none of it was visible, so a card about the weather was something you could only take on trust. A warning you cannot check is one you stop believing the first time it looks wrong. **Which number leads depends on what triggered it.** If the warning is about warm nights it leads with the night figure, because that is the surprising half — a night that never cools is harder on a plant than a hot afternoon, and the daytime high would point you at the wrong thing. **And from 20 August 2026 a hot spell can reach your phone too**, not just the card — see [Hot spell alerts](/help/hot-spell-alerts/). Until then heat was something you only found out about by opening the app, which is no use to somebody already outside in it. **Still to come:** somewhere to see the next few days at a glance. This fixes the card that made the complaint; the wider view is a separate piece of work.
It warned me about cold nights but said nothing is at risk. Which is it?
**Both, and they are different things — the wording was broken for two crops until 24 August 2026.** There is a kind of cold that ruins part of your harvest without endangering the plant at all: nights in the forties and low fifties, well above freezing. Nothing dies. But a tomato stops setting fruit, a bok choy decides winter has been and gone and runs to seed, and a basil comes through looking rough. Those three want completely different things from you, so the card says which one it is: - **It will stop setting fruit.** Pure reassurance. The flowers drop, the plant is fine, you did not cause it, and it starts again on its own when the nights come up. There is nothing to do. - **It will run to seed.** The opposite — this is a deadline. The leaves turn bitter and stop coming, and it does not undo itself. Pick what you want in the next day or two. - **It will come through fine, but what you pick may not be its best.** Quality, not survival. It comes right when the nights warm. **What was broken:** the card only knew the first two. For eggplant and basil — the third kind — it printed a fragment reading *"and undefined will stop setting fruit"*, which was a broken sentence and also the wrong advice, since neither of them stops setting fruit from cold. Two of the six crops we hold this data for. **Why only six crops:** this needs a source that names a temperature and a specific harm in the same breath, and that is a rare thing for a university to publish. Where we do not have it we say nothing, which means a quiet night is not proof your plant is unaffected.
I garden in two places. Does the alert know they have different weather?
**From 26 August 2026, yes. Before that it did not, and it mattered.** The app used to look up tonight’s low for **one** of your gardens — whichever came back first, with no rule about which — and then check **every plant you own, in every plot,** against that one number. ⚠ **That is not simply the second plot going unwatched.** A plot in a valley and a plot up a hill can differ by several degrees on a clear night. Judged by the wrong one, you would get **a warning about plants that were never at risk**, or worse, **silence about plants that froze.** Now each garden is checked against the forecast for where it actually is, and only the plants standing there are judged by it. **You still get one alert a night, not one per plot** — the frost alert gathers what is at risk across your gardens and names the coldest of the places that actually had something at risk. **The hot-spell alert works slightly differently and it is worth knowing:** each garden is assessed on its own, but the message describes **one** of them — whichever spell starts soonest. A heat warning carries a peak temperature, a start day and a length together, and blending two places would give you a peak from one garden beside a start day from the other — **a sentence that is true of neither.** The other plot is still assessed correctly and warns on its own day.
How do I turn alerts off?
**Profile → Alerts → Turn alerts off on this phone.** It unsubscribes the device you are holding and tells our server to forget it, so nothing further is sent to it. It says *this phone* deliberately: if you have the app on a tablet as well, that one keeps its own setting and you turn it off there separately. Until 13 August 2026 **there was no way to turn them off from inside the app at all** — the code to do it existed and nothing had ever called it, so the only route was your browser or phone settings. That was a permission you could grant and never withdraw, which is not a choice.
I asked about my first frost on the day it was due and the app talked about it in the past. What happened?
A counting bug, fixed on 8 August 2026. When you asked, the app worked out how many days away your first frost was and then chose its wording — more than zero days meant "from today", anything else meant "ago". Nobody wrote the case for zero. So on the one day of the year when the answer is go and cover them tonight, it said the frost was "0 days ago" and talked about it as something that had already happened. It was wrong for exactly one day each autumn, and that day was the one that mattered. Every autumn timing answer hangs off that number, so it was worth fixing properly rather than patching the sentence.
Why did some of my plants get a warning and others did not?
Because frost does different things to different plants. A tomato at 29°F is finished. Kale at 29°F is arguably improved — frost sweetens it. GardenTrack only warns about plants the forecast will actually harm, which means most nights most of your garden gets no warning at all. That silence is deliberate. **Where the plant is standing also counts, and until 17 August 2026 it did not.** A seed tray is indoors, so tonight's low outside does not reach it — and the app was warning about trays anyway, including in the notification it sends to your phone after dark. *"Tonight ends the tomato seedlings"*, about a tray on a kitchen windowsill. Trays are now left out of the frost, heat and cold warnings entirely. **A tray you have carried outside for hardening off is a different matter and has always had its own alert** — that one knows the temperature each crop can actually take and tells you to bring it in. **What has NOT changed: a pot still gets warned.** A potted tree on a porch is exactly the plant a frost kills, and because you can pick it up, "bring it in" is something you can actually do tonight. A plant under glass gets warned too — a greenhouse buys you a few degrees, not immunity, and we have no way to know whether yours is heated. (Until 23 August 2026 *a greenhouse* was one of the answers to what a plant is planted in; it is not any more, because it named a roof rather than what the roots are in. Nothing about this warning changed — the pot or the bed under that glass gets warned for exactly the same reason.) And a plant whose position you have not given us gets the warning too: not being asked is not the same as being safe.
Where does the forecast come from?
The US National Weather Service. It is free, public, and updated roughly hourly. We look up the grid square your garden sits in and cache the answer, so a whole town's worth of gardeners is one lookup rather than thousands.
How does it decide a plant will die?
Mostly from two things: how frost-tender the crop is, and whether losing the top of the plant ends it. A tender annual is finished by a hard frost. A tender perennial drops its leaves and its fruit and comes back. For about 40 crops we also hold a real temperature from a university source, and we use it — but only when it is about a part of the plant that is out there tonight. An apple's 28°F is about open blossoms, so it speaks in April and stays quiet in January.
Why did the app warn me about my apple tree, which is supposed to be hardy?
Because the tree is hardy and the flowers are not. A dormant apple shrugs off 20°F; its open blossoms are dying at 28°F, and one cold night in bloom can take the whole year's fruit. The same goes for pears, plums, apricots, cherries, peaches, blueberries, strawberries and raspberries. If we only went by how tough the plant is, we would say nothing at all on the one night that costs you the crop.
Will it warn me if I am somewhere without coverage?
No. The forecast source covers the United States. Outside that we say nothing rather than guess, which is the honest answer but not a useful one. International coverage needs a different weather source and is not built.
The app says nothing about frost. Is it broken or is it just warm?
Fair question, and one we take seriously — this exact feature shipped in a state where it could never fire and nothing looked wrong. Check the frost card is not simply absent because tonight is mild. If you seed a cold night and still see nothing, tell us.
What does the notification actually say?
The temperature is the headline — "29°F tonight" — because that is the fact that makes you move. Underneath, which plants are at risk and the two things you can do: cover them, or pick what is on them. It never says our name or that it is a notification; your phone already prints both above the message, and spending the most-read line repeating them would be a waste of the one thing you read at a glance.
Does it work offline?
The last forecast it fetched is stored on your phone, so a warning you already have survives losing signal. A forecast more than twelve hours old is treated as unusable and the app goes quiet rather than acting on stale weather.

More on this

Shipped 2026-07-30. Last checked 2026-08-26. Something here wrong or out of date? Tell us — support docs going stale is a bug.