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Last and first frost dates in San Juan

Argentina

In San Juan the last spring frost usually comes around 27 July and the first autumn frost around 20 June, which leaves about 328 frost-free days (median of 2016–2025). Tomato seedlings can go into open ground from 29 August to 28 February.

Last spring frostaround 27 July
First autumn frostaround 20 June
Frost-free days328 days

Median of 2016–2025 for the 25 km grid cell of the city: the last day at or below 0 °C in spring and the first in autumn (ERA5 reanalysis via Open-Meteo). In a cold year a frost can come a week or two later — Greenly warns 48 hours ahead.

When is the last frost in San Juan?

The last frost in San Juan usually comes around 27 July: that is the median of 2016–2025, so in about half of those years the last night at or below 0 °C came later. Hardy crops start before it and frost-tender ones only after it: in the table below arugula can go into open ground from 6 July, while corn waits until 15 August. The first autumn frost follows around 20 June, about 328 days later: harvest or cover frost-tender crops before then.

When to sow and plant

CropSow for seedlingsPlant out in a greenhouseOpen ground
Achocha3 June – 11 March13 July – 20 April3 August – 20 April
Ageratumfrom 13 June—from 29 August
Arugula——sow 6 July – 15 May
Basil21 July – 17 April28 August – 25 May18 September – 25 May
Beet——sow 6 July – 20 April
Bell Pepper29 June – 30 December28 August – 28 February18 September – 28 February
Black-eyed Susanfrom 12 May—from 3 August
Bok Choy8 June – 28 April13 July – 2 June3 August – 2 June
Borage——sow 3 August – 25 April
Broad bean——sow 6 July – 11 March
Broccoli——sow 6 July – 4 March
Brussels Sprouts1 May – 31 January15 June – 16 March6 July – 16 March
Busy Lizziefrom 11 May—from 3 August
Cabbage——sow 6 July – 10 February
Calendula——sow from 6 July
Carrot——sow 6 July – 27 March
Cauliflower4 May – 4 March15 June – 15 April6 July – 15 April
Celeriac27 April – 31 December13 July – 17 March3 August – 17 March
Celery27 April – 10 January13 July – 27 March3 August – 27 March
Celosiafrom 4 Julyfrom 18 Augustfrom 8 September
Chamomile——sow 6 July – 15 April
Chayote28 April – 24 December25 July – 21 March15 August – 21 March
Chickpea——sow 6 July – 1 March
Chicory21 May – 26 March—6 July – 20 April
Chili Pepper29 June – 5 February28 August – 5 April18 September – 5 April
China asterfrom 7 Julyfrom 28 Augustfrom 18 September
Chives——sow 6 July – 6 April
Cilantro——sow 6 July – 16 April
Corn——sow 15 August – 1 March
Corn poppy——sow from 6 July
Cosmosfrom 4 Julyfrom 18 Augustfrom 8 September
Cucumber31 July – 7 March28 August – 4 April18 September – 4 April
Daikon——sow 6 July – 13 April
Delphiniumfrom 17 April—from 6 July
Dill——sow 6 July – 26 April
Edging lobeliafrom 11 May—from 3 August
Eggplant29 June – 30 December28 August – 28 February18 September – 28 February
Florence fennel29 May – 11 March13 July – 25 April3 August – 25 April
Foxglovefrom 30 March—from 6 July
Garden sorrel——sow 6 July – 14 April
Green Beans——sow 8 September – 9 March
Hollyhock——sow from 6 July
Hyssop——sow 6 July – 7 March
Kale——sow 6 July – 8 April
Kiwano7 July – 14 March8 August – 15 April29 August – 15 April
Kohlrabi——sow 6 July – 18 April
Leek6 April – 22 December15 June – 1 March6 July – 1 March
Lemon balm——sow 6 July – 10 April
Lettuce——sow 6 July – 23 April
Lisianthusfrom 20 Marchfrom 15 Junefrom 6 July
Lovage——sow from 6 July
Luffa17 July – 7 January28 August – 18 February18 September – 18 February
Marigoldfrom 1 Junefrom 13 Julyfrom 3 August
Marjoram29 June – 26 March—18 September – 25 May
Melon31 July – 23 February28 August – 22 March18 September – 22 March
Microgreens——sow 8 September – 5 June
Moringa12 July – 31 March5 September – 25 May26 September – 25 May
Moss rosefrom 18 May—from 3 August
Mustard greens——sow 6 July – 5 May
Napa cabbage10 June – 5 April13 July – 8 May3 August – 8 May
Nasturtiumfrom 5 Junefrom 13 Julyfrom 3 August
Okra17 July – 19 March28 August – 30 April18 September – 30 April
Oregano16 April – 16 March15 June – 15 May6 July – 15 May
Pansyfrom 20 Aprilfrom 15 Junefrom 6 July
Parsley——sow 6 July – 4 April
Parsnip——sow 6 July – 22 February
Peanut22 July – 13 February28 August – 21 March18 September – 21 March
Peas——sow 6 July – 6 April
Petuniafrom 26 Junefrom 28 Augustfrom 18 September
Physalis24 June – 10 February8 August – 26 March29 August – 26 March
Pumpkin17 July – 12 January28 August – 23 February18 September – 23 February
Purple coneflowerfrom 14 April—from 6 July
Radish——sow 6 July – 20 May
Sage27 April – 12 March15 June – 30 April6 July – 30 April
Scarlet sagefrom 17 June—from 29 August
Snapdragonfrom 11 Aprilfrom 15 Junefrom 6 July
Soybean——sow 18 September – 31 March
Spinach——sow 6 July – 25 April
Stevia20 June – 1 February8 August – 21 March29 August – 21 March
Stock——sow from 6 July
Sunflower——sow from 8 September
Sweet alyssum——sow from 6 July
Sweet Corn6 July – 26 March28 July – 17 April18 August – 17 April
Sweet peafrom 4 Mayfrom 15 Junefrom 6 July
Sweet William——sow from 6 July
Swiss Chard——sow 6 July – 20 April
Thyme——sow 6 July – 1 March
Tomato17 June – 7 January8 August – 28 February29 August – 28 February
Turnip——sow 6 July – 22 April
Watercress——sow 6 July – 3 May
Watermelon31 July – 11 February28 August – 10 March18 September – 10 March
Zinniafrom 1 Augustfrom 5 Septemberfrom 26 September
Zucchini7 August – 12 March28 August – 2 April18 September – 2 April

Planting out: a week after the last frost once the soil is warm enough for the crop; frost-hardy crops three weeks before it; an unheated greenhouse three weeks earlier. Seedlings are sown so they are ready on that day. Each window starts on the Greenly calendar date and ends on the last day that still leaves the crop’s days to harvest (from its card) before the average first autumn frost, plus six weeks of picking for crops harvested over weeks (tomatoes, peppers, aubergines, cucumbers, courgettes, pumpkins, watermelons, beans) — our rule; earlier in the window is safer.

When the soil warms up in San Juan

The day the top 7 cm of soil first averages each temperature over a week, median of 2016–2025 (ERA5 via Open-Meteo). The soil reaches 10 °C same day the last spring frost and 15 °C 33 days after it.

SoilDateAgainst the last spring frost
5 °Calready in the first week of July—
10 °C27 Julysame day
15 °C29 August33 days later
18 °C18 September53 days later

Frost dates near San Juan

Of the nearest cities on our list, the last spring frost ends earliest in La Rioja (17 July) and latest in Los Andes (24 August).

CityDistanceLast spring frostFirst autumn frost
Mendoza153 km10 August17 June
Los Andes242 km24 August5 June
Ovalle275 km——
San Luis284 km21 August23 June
La Rioja286 km17 July15 June

Seeds, seedlings and markets in San Juan

Within 15 km of San Juan OpenStreetMap lists 9 garden centres, 5 farm-supply shops, 3 plant nurseries and 6 markets (collected 27 October 2026). The nearest garden centre to the city centre is Vivero Regalería Verde, 2 km away.

Places: © OpenStreetMap contributors, ODbL.

What to grow at home in winter in San Juan

Frosts in San Juan usually come from about 20 June to about 27 July. These plants have indoor care in their Greenly cards and are harvested quickly, so they can be sown on a windowsill in winter.

Weather in San Juan by month

Average weather in San Juan over 2016–2025: the warmest month is January. Months that average 20 °C or more by day: September–April (23.7–34.2 °C). Months that average 30 °C or more by day: November–March (30–34.2 °C). No month averages below 0 °C at night; the coldest nights, in July, average 3 °C. About 130 mm of rain falls in a year, on 25 days; January is the wettest month (27 mm) and July the driest (2 mm).

MonthDay, °CNight, °CRain, mmRainy days
January34.221.8275
February33.320.9153
March3017.8173
April24.713.192
May19.18.372
June15.4441
July15.4321
August19.95.9111
September23.79.341
October27.413.1152
November31.717.851
December3420.3143

Average of the daily highs and lows, rain per month and days with at least 1 mm (ERA5 via Open-Meteo, the same grid cell as the frost dates).

Planted in autumn

CropWhen to plant
Bearded Irisby 21 May
Crocusby 21 May
Daffodilby 21 May
Garlic21 May – end of June
Grape hyacinthby 21 May
Helleboreby 21 May
Hyacinthby 21 May
Lilyby 21 May
Ornamental onionby 21 May
Peonyby 21 May
Saffronby 21 May
Snowdropby 21 May
Tulipby 21 May
Wild garlicby 21 May

From a month before the first autumn frost, so the roots grow before winter, to the late-planting limit on each crop’s page (about two weeks before the ground freezes, by ten years of weather).