Rising on Wikipedia this October: readers of the English article on frost went from 938 in the first week of September to 1,484 in the week to 20 October, as the first cold, clear nights arrive.
What to cover, bring in or drain before the first frost
Type the forecast lows for the next nights and list what is outside. The page estimates how cold it gets at ground level, and shows which things cross their threshold on which nights. One run writes the plan: an alert rule for each thing, a card for each night and a note for tonight.
1 The next nights
2 What is outside
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3 The week, night by night
The cloche bed
A glass cloche marks every night a thing crosses its threshold.
Ground estimates and thresholds are rough rules of thumb, not a forecast: clear, calm nights and low spots often run a few degrees colder than the forecast low, and cloud, wind, walls and height keep it milder.
4 Write the plan
One run writes an alert rule for each thing (when to act, what to do, when to undo it), a card for each night, a note for tonight you can stick on the fridge, a short kit list and what to watch.
The verdict follows a fixed rule, checked in order: act tonight if anything crosses its threshold on the first night; act later this week if anything crosses it on a later night; all clear otherwise.
5 Your weeks
How the page works it out
Each night's ground estimate starts from the forecast low and adds rough adjustments, in °C (double them in °F): a clear sky -2, partly cloudy -1, cloudy or wet 0; calm -1, a light wind 0, breezy +1, windy +2; a low spot -1, an open garden 0, a sheltered courtyard or a balcony +1. Risk by the ground estimate: frost possible at 2°C (36°F) or below, frost at 0°C (32°F) or below, a hard freeze at -3°C (27°F) or below. Each thing acts at its own threshold: frost-tender plants 2°C (36°F), car glass 1°C (34°F), half-hardy plants and anything not recognised 0°C (32°F), water -1°C (30°F), pots -2°C (28°F), hardy plants -4°C (25°F). These are estimates, not a forecast - a local frost warning always wins.