# First Frost

> A one-week frost planner for a garden, yard or balcony. Type the forecast low for each of the next nights with the sky and wind, choose where your things are, and list what is outside. The free side runs in the browser: a rough ground-level estimate and frost risk for every night, the kind and threshold of each thing, a cloche bed of the nights each crosses its threshold, and a verdict by a fixed rule. One metered reply writes the plan: an alert rule per thing (when, what to do, when to undo it), a card per night, a note for tonight, a short kit list and what to watch.

App: https://first-frost.skillsafe.ai/
API tutorial: https://first-frost.skillsafe.ai/api.html

## Why it exists

The first frosts of the season arrive in the northern hemisphere in October and November. In October 2026, readers of the English Wikipedia article on frost rose from 938 in the first week of September to 1,484 in the week to 20 October. The hard part is not knowing frost exists; it is knowing which of the things outside need doing on which night, because a clear, calm night can run colder at ground level than the forecast low. First Frost makes that quick.

## What the free side does

- One night per line ("Tue 3 clear calm", "Mon H:52 L:31", "Tonight: Low around 28. North wind 5 to 10 mph."): the forecast low is the number after "low", "lo", "min" or "L:" if there is one; else the lowest of two or more degree readings, the lower end of a range ("28-34"), or the last number. Percentages, wind speeds and rain amounts are never read as the low. A wind speed with no wind word sets the wind (under 3 mph calm, up to 10 light, up to 18 breezy, else windy). The night's name is what comes before the low (or before a colon). Up to 7 nights. A Celsius low of 20 or more, or a Fahrenheit week with every low at 10 or below, gets a check-the-units warning.
- Ground estimate = forecast low plus rough adjustments, in degrees C (double them in F): clear -2, partly cloudy -1, cloudy or wet 0; calm -1, light wind 0, breezy +1, windy +2; low spot -1, open garden 0, sheltered courtyard or balcony +1.
- Risk by the ground estimate: frost possible at 2C (36F) or below, frost at 0C (32F) or below, hard freeze at -3C (27F) or below.
- One thing per line, up to 8 (a line like "Dahlias, potted lemon tree, outdoor tap" whose parts are each recognised is read as separate things, with a note). Kind by keywords, or set it by ending a line with ", tender", ", hardy", ", water" or ", pot" ("very tender", "half hardy" also work). Thresholds: frost-tender 2C (36F), car glass 1C (34F), half-hardy and unrecognised 0C (32F), water -1C (30F), pots -2C (28F), hardy -4C (25F).
- The verdict, checked in order: act tonight - something crosses its threshold on the first night; act later this week - something crosses it on a later night; all clear - otherwise.
- All of these are rough rules of thumb, not a forecast. A local frost warning always wins.

## The paid reply

One JSON object: verdict (act_tonight | act_this_week | all_clear), title, summary, tonight, rules (one {item, when, action, undo} per thing, in order), nights (one {night, card} per night, in order), kit (up to 6 supplies) and watch_note. It uses only what you enter: no invented plants, places, buildings, weekdays or weather, no number that is not in your week, and only ordinary, safe protection (no heaters, flames, salt or chemicals). The page re-checks every reply against the rule and those limits.

## Exports

Markdown, JSON, the cloche bed as CSV (one row per thing, one column per night) and a late-afternoon calendar reminder (.ics) on each night that needs action. Kept weeks go to a list in your SkillSafe account (opt-in).

## Source

Built on the SkillSafe skill @claude-office-skills/weather-automation (https://skillsafe.ai/skill/@claude-office-skills/weather-automation) - weather-based workflows: forecasts, alert rules with thresholds and notifications - applied to one household's cold week. The reply runs on gpt-terra and is metered per run.