At what temperature can I put my plants outside?

Nights consistently above 10 °C, which is 50 °F, is the line our cold alert uses and the one most sources land on. Treat it as a floor rather than a target: a run of nights at 11 °C is legal by that rule and still cold for a tropical plant that spent the winter in a heated room.

Do I have to harden plants off, or can they go straight out?

Give them shade first. The light difference between a sill and open sky is larger than the difference between any two windows in your home, so a plant that was comfortable indoors can be over its limit outdoors on day one. A shaded spot for the first week costs you nothing.

Which houseplants should not go outside at all?

The ones whose published light needs are low. In the table above the shade-tolerant favourites score worst in the open, and the succulents and high-light plants score best. That is the opposite of the usual tough-plant intuition, and it is because toughness indoors usually means tolerance of dimness.

Why does my plant dry out so much faster outside?

Because outside there is wind, a real gap between day and night, and unfiltered sun, and a room has none of the three. Our watering model follows that by dropping the room conversion it applies indoors: outdoors it takes the forecast as it comes, and a balcony sits between the two at a fifth off.

Does GrowSpot warn me about rain and wind once the plant is outside?

Yes, and only then. Heavy rain, high wind and heavy snow are raised for outdoor plants alone, since a wall stops all three. Heat and cold are raised either way, because a cold snap still reaches a plant standing at the glass.

Can plants get sunburned?

Yes. The photo above is one of ours: a monstera burned at an indoor window, outer leaves bleached to yellow with dried brown edges while the shaded leaves behind them stayed dark green. Light damage lands where the light does. Moving out is the classic trigger because the jump is bigger than it feels: the north-side spot in the table above goes from 3,640 lux indoors to 12,000 in the open. Bleached leaves do not turn back, so the hardening-off schedule above is how you avoid burning more of them.

When to Put Plants Outside

Wait until nights are reliably above 50 °F, says the summary at the top of this search, and the horticultural society under it agrees. In Celsius that is 10 degrees, which is the same number our cold alert uses. We did not copy it: our threshold started at 4 °C and a horticulture review moved it up, on the grounds that tropical foliage starts suffering around 10 to 12 rather than at freezing.

So the temperature half is settled, and it is worth saying plainly that this is a forecast question rather than a date question. There is no month at which it becomes safe, and no last-frost date that applies to a flat in a different hemisphere. What matters is the run of nights ahead of you.

The number itself is not as settled as it looks. Five extension services cover the same move, and the ones that give it split ten degrees apart — and every one of them attaches an instruction about light, which is the half this page is about.

Published by	The night-time number	What else it tells you to do
yardandgarden.extension.iastate.edu	Above 50 °F	“wait until nighttime temperatures are consistently and reliably above 50°F before moving houseplants outdoors”. On light: “Never move houseplants from indoors into full sun”, and “introduce more light over 10 to 14 days”.
planttalk.colostate.edu	Above 50 °F	“wait until night temperatures are above 50 degrees Fahrenheit and all danger of frost has passed”. On light: “Harden off plants by placing them in a shaded area for a few days and gradually exposing them to longer periods of sun”.
extension.umd.edu	Above 60 °F	“Put your plants out only after night temperatures remain above 60°F (usually mid-May or early June).” On light: “Acclimate plants to increased light by placing them in a shady area outdoors”, over “a period of two weeks”.
hgic.clemson.edu	Above 60 °F	“To be safe, wait until temperatures moderate in the spring and consistently exceed 60 ° F at night.” On light: “Gradually expose them to sunlight by placing them in deep shade under a tree for a few days”.
site.extension.uga.edu	No number given	Only the light instruction, and it names the plant in our own table: “a shade loving peace lily should not find itself in full sun out on the sidewalk.”
site.extension.uga.edu	A week or two	“Let the plant adjust to the new temperature, humidity, and brighter light conditions for a week or two before moving it to its final location for the summer.”

Five extension services on the same move, copied exactly as each writes it. They split ten degrees apart on the temperature, and every one of them also gives an instruction about light. 6 figures transcribed from 5 sources, read end to end on 30 August 2026. Units are copied exactly as each source writes them; nothing here is converted, and nothing here is our own measurement. All of them, from every page, are one free download.

What the light does when you open the door

Here is the part the temperature answer leaves out. Take one peace lily and one bright-but-shaded exposure, and walk it through the doorway without changing anything else. This is the gentle version of outdoors, shade rather than sun:

About a dozen potted foliage plants standing on a paved forecourt against a plain wall, all of them in open shade with no direct sun falling on them — Open shade outdoors, with no sun touching any of them. This is the spot the readings below argue for, and it is still far brighter than the sill they came from.

Where it is standing	Estimated light	Verdict
Indoors, at the window	3,640 lux	Great fit, 99/100
On a balcony, in open shade	7,000 lux	Worth a try, 65/100
Outdoors, in open shade	12,000 lux	Not the best fit right now, 44/100

One peace lily, one exposure, three sides of the same doorway. The spot is what moves here. What does not: the same plant, the same bright-but-shaded exposure on a clear day, with 24 °C, 55% humidity and light airflow on every row.

Shade outside is already brighter than the sill it left, and the verdict has flipped. And that was the gentle version: the same model puts an unshaded midday spot at 80,000 lux, close to seven times the shaded row above. That gap, rather than the night-time temperature, is what damages plants in their first week out. And it does not take open sky to do it:

A Monstera adansonii on a moss pole by a window. The outer leaves are bleached to yellow with brown dried tips and margins, while the shaded leaves behind them stay dark green. — One of our own plants, burned by sun at an indoor window. The outer leaves are bleached to yellow and dried brown at the tip and edge; the shaded leaves right behind them are untouched. That is the tell: light damage lands where the light does, not evenly over a plant.

Our page on how bright a room can actually get works the indoor ceiling out in detail.

What our own meter says, across 204 readings

Everything above is our light model estimating. This is not: these are medians of readings taken with the app’s meter, on 104 different spots across 36 days. The full spread, quartiles and tier counts are published as open data on our indoor light measurements page.

Where the reading was taken	Median reading
Indoors (49 readings, 40 spots)	2,349 lux
On a balcony (25 readings, 17 spots)	8,173 lux

Median of readings taken with the app’s light meter, grouped by where the reading was taken. How this was measured → The full indoor light dataset →

A balcony reads about 3.5 times the median indoor spot. That is measured rather than modelled, and it is not the same comparison as the table above: those rows hold one exposure constant, where these readings pool every orientation, hour and sky people take them in. Held constant, the model puts a balcony at about 1.9 times the sill. Across real homes the gap comes out wider. We are not publishing a figure for fully open ground, because we only have three readings marked that way, and three is not a number to draw a line through.

Five plants, one open spot

Now set five plants down in that unshaded midday spot, the one at 80,000 lux. The split does not follow the tough-plant reputations:

The plant you carry out	What the light is doing	Verdict
Peace lily	Too bright here	Not the best fit right now, 34/100
Monstera	Too bright here	Not the best fit right now, 39/100
Snake plant	Too bright here	Not the best fit right now, 35/100
Jade plant	Just the right amount of light	Good fit, 82/100
Aloe vera	Just the right amount of light	Good fit, 82/100

Five plants set down in the same open spot, reading the identical light. Only one thing moves down the table. The spot itself does not: one open spot on a clear summer day, with 24 °C, 55% humidity and strong airflow held the same on every row. The middle column is only what the light is doing. The verdict is the whole spot, so a plant can have the light it wants and still lose points on warmth, humidity or airflow.

Every row read the identical light in the identical spot, and the split is clean rather than gradual: the two succulents are comfortable, and the three that get recommended for low corners are all past their limit. Toughness indoors usually means tolerance of dimness, which is the opposite of what an open sky asks for. Shade outdoors is the fix, and it is not the same thing as shade indoors.

The watering changes at the threshold too

There is a third change, and it happens the moment the pot is on the other side of the door. Indoors, our watering model does not use the weather as it arrives: it converts the forecast day into a room equivalent first, pulling the temperature toward a room baseline, flattening the daily swing, and taking the air as still and the light as overcast. On a balcony it uses the forecast day itself, discounted for shelter at ×0.8 on the reasoning that a balcony usually has a roof, a wall, or both. Out in the open it uses the day as forecast with nothing taken off it: the real wind, the real swing between day and night, and the real sunshine.

A row of potted plants standing along a balcony parapet under a deep roof overhang, with the flat's windows and door behind them — The sheltered version of outdoors: a roof over the pots and a wall behind them. That shelter is the ×0.8 in the paragraph above, and it is still brighter than the sill on the other side of that glass.

Rain, wind and snow alerts work the same way: they exist only for a plant that lives outdoors, because a wall stops all three. Heat and cold are the two that follow a plant indoors, and the five events and their thresholds are set out on the page for the journey in the other direction.

What to do with yours

Watch the nights rather than the calendar, and give it a week of shade outdoors before anything sunnier. Take a reading in the spot you are actually planning to use, with the free spot checker if you would rather not install anything, and take it at the time of day the plant will be sitting there. Then expect to water more often than you did indoors, because the room conversion stops at the door rather than because the plant is thirstier, and read what else moves that interval before you change anything else. A summer outside also settles the feeding question, since the light half of that test is cleared by open sky on any day of the year.

The verdicts here come from the same spot check the app runs, with temperature, humidity and airflow held at one set of values so the only thing moving is the one named in each table. Light figures are estimates for a clear day rather than meter readings, and the balcony discount is a calibrated model constant rather than a measurement of your balcony.

By GrowSpot · Published August 15, 2026 · Last updated August 30, 2026

Plant photo credits