Winter squash · Wheaton, Illinois, United States
When to plant winter squashes in Wheaton
Main outdoor window
29 May - 12 Jun
A climate estimate. Check your soil, forecast and cultivar.
Timed from last spring frost
26 April
In Wheaton, on your chosen risk.
Ready to pick
17 Aug - 16 Sep
If you plant at the start of the window.
The average last frost. Half of all years are later than this.
Step by step in Wheaton
Download these planting dates (.ics)
Import into Apple Calendar, Google Calendar or Outlook. Dates use the selected risk level and are planning estimates, not frost alerts.
Each window is a planning range. Check the forecast, soil and cultivar before planting; a later date is not automatically safer in hot or wet conditions.
Start indoors
5-19 Apr
Three weeks before your last frost, under cover or on a windowsill.
Sow direct
29 May - 12 Jun
Delayed by a soil-warming estimate derived from historical air temperatures. The frost-only date would be 10 May. Measure your soil before planting.
Plant out
29 May - 12 Jun
Delayed by a soil-warming estimate derived from historical air temperatures. The frost-only date would be 10 May. Measure your soil before planting.
Harvest
17 Aug - 16 Sep
Winter squashes through the year
Against the frost risk in Wheaton
Seasonal context
Rainfall and the growing season in Wheaton
May has the highest average precipitation (121 mm); January has the lowest (44 mm). Compare this pattern with the planting windows and your water supply.
During wetter months, check that beds and containers drain after heavy rain. During drier months, plan how you will keep seeds and new transplants watered. Monthly averages can hide long dry spells and intense storms; they do not show soil moisture, humidity or this week's weather.
Source: NASA POWER, corrected MERRA-2 precipitation, 2001–2020. Values are approximate monthly totals, including the water equivalent of snow, from the nearest 0.5° × 0.625° grid cell. This reference period differs from the temperature record. Rainfall provides context and does not change the calculated planting dates. Method and limitations.
Monthly growing conditions in Wheaton
Compare the planting window with the local temperature pattern. These are historical monthly averages, not this year's forecast or measured soil temperatures. Average frost days do not tell you whether a particular night will freeze.
| Month | Average low | Average high | Frost days |
|---|---|---|---|
| January | -9.8°C (14.4°F)14.4°F (-9.8°C) | -1.5°C (29.3°F)29.3°F (-1.5°C) | 29.4 |
| February | -8.2°C (17.3°F)17.3°F (-8.2°C) | 1.1°C (33.9°F)33.9°F (1.1°C) | 26.6 |
| March | -2.4°C (27.6°F)27.6°F (-2.4°C) | 7.7°C (45.9°F)45.9°F (7.7°C) | 23.1 |
| April | 2.6°C (36.7°F)36.7°F (2.6°C) | 14.5°C (58.1°F)58.1°F (14.5°C) | 8.7 |
| May | 8.8°C (47.8°F)47.8°F (8.8°C) | 20.7°C (69.3°F)69.3°F (20.7°C) | 0.3 |
| June | 14.7°C (58.5°F)58.5°F (14.7°C) | 26.3°C (79.3°F)79.3°F (26.3°C) | 0.0 |
| July | 17.6°C (63.8°F)63.8°F (17.6°C) | 28.7°C (83.6°F)83.6°F (28.7°C) | 0.0 |
| August | 17.2°C (63°F)63°F (17.2°C) | 28.3°C (83°F)83°F (28.3°C) | 0.0 |
| September | 12.9°C (55.2°F)55.2°F (12.9°C) | 24.7°C (76.4°F)76.4°F (24.7°C) | 0.0 |
| October | 5.9°C (42.7°F)42.7°F (5.9°C) | 17°C (62.6°F)62.6°F (17°C) | 3.2 |
| November | -0.7°C (30.7°F)30.7°F (-0.7°C) | 8.4°C (47.2°F)47.2°F (8.4°C) | 18.0 |
| December | -6.3°C (20.6°F)20.6°F (-6.3°C) | 1.4°C (34.5°F)34.5°F (1.4°C) | 27.5 |
For winter squashes, also check drainage, sunlight and cultivar requirements. See the rainfall context above; humidity, irrigation and local pest pressure are not calculated.
Local growing check
Before choosing winter squashes for Wheaton
- May is the wettest month in the rainfall grid, averaging about 121 mm. Check how your own bed drains and plan watering around actual soil moisture; monthly rain totals are not an irrigation schedule.
The temperature and rainfall tables on this page show the underlying climate estimates. How these suitability checks work · Record what happens in your garden.
Before you plant winter squashes
Use the calendar to plan ahead, then check the conditions in your own garden.
- Measure the soil at sowing depth. Aim for at least 18°C (64.4°F); the calendar estimates soil warmth from air temperatures and cannot measure your bed.
- Check the local overnight forecast before planting out. Delay planting or keep protection ready if frost is forecast, even after the historical last-frost date.
- Harden off plants raised indoors: gradually expose them to outdoor light, wind and temperature before their final move into the bed.
- Use the maturity range on your seed packet when choosing a variety. Cold, short days and transplant stress can make harvest later than the calendar estimate.
Choose a squash that can mature before the season ends
Allow room for vines and provide warm, drained soil with steady moisture during establishment and fruit growth. A vigorous commercial variety can overwhelm a small bed even when its fruit seems an attractive size.
Let storage fruit reach maturity before cutting, leaving an intact stalk and avoiding bruises. Follow the cultivar's curing and storage guidance, and use damaged fruit promptly rather than storing it with sound squash. Record mature fruit separately from small late-set fruit.
What to record this season
How many fruit reached storage maturity before cold or persistent wet weather? Add the cultivar, sowing date and conditions to your growing record so you can compare next season.
Further reading: RHS squash growing guide . General crop guidance; local dates on this site are calculated separately. Source checked 19 September 2026 by Safe to Plant; this is not an expert review.
The RHS reference is written for UK growing conditions. Use its cultivation advice with local seasonal guidance; UK sowing months are not worldwide planting dates.
How the dates are calculated and their limits · Keep a growing record · Report a local discrepancy
Why these dates
Allow room for vines and provide warm, drained soil with steady moisture during establishment and fruit growth. A vigorous commercial variety can overwhelm a small bed even when its fruit seems an attractive size.
Check the named variety and local forecast before exposing young growth. The catalog cold-damage figure is a reference, not a guarantee: plant age, acclimatisation, wind and the duration of a freeze affect damage.
This calendar uses frost-relative offsets as a starting point. Winter squashes are timed from 3 weeks before that frost for an indoor start, with planting out 2 weeks after it, and this page simply resolves those offsets against the frost date computed for Wheaton.
The calendar also applies a soil-warming estimate derived from historical air temperatures. Where that estimate is later than the frost-based date, it delays the window. Soil in your own garden can warm earlier or later; a thermometer at sowing depth is a better final check. Cold, wet conditions can slow germination and increase decay risk.
The median frost-free season here is 179 days, against 80 to 110 days to maturity for this crop counted from sowing. That margin is what decides whether a late sowing is worth attempting.
Nearby
Winter squashes in places close by
Also in Wheaton
Other vegetables to time
Growing winter squashes in Wheaton
Can I grow winter squashes in Wheaton?
The calendar estimates a planting window, not a guarantee of success. May is the wettest month in the rainfall grid, averaging about 121 mm. Check how your own bed drains and plan watering around actual soil moisture; monthly rain totals are not an irrigation schedule.
When should I plant winter squashes in Wheaton?
Aim for 29 May - 12 Jun in an average year. If you would rather not gamble on the weather, wait until 28 May - 11 Jun - by then frost has finished in nine years out of ten.
Can I plant winter squashes earlier in Wheaton?
The historical frost estimate is 10 May. For Winter squashes, an air-temperature model estimates soil warmth of about 18°C (64.4°F) around 29 May. This is not a soil measurement or a forecast. Check your bed at sowing depth; cold, wet conditions can slow growth and increase decay risk.
When might winter squashes be ready to harvest in Wheaton?
The estimated period is 17 Aug - 16 Sep, based on 80 to 110 days from the modeled planting date. Cultivar, planting material and growing conditions can change this interval; check the plant as well as the calendar.
How much frost will winter squashes tolerate?
Check the named variety and local forecast before exposing young growth. The catalog cold-damage figure is a reference, not a guarantee: plant age, acclimatisation, wind and the duration of a freeze affect damage.