USDA Hardiness Zone 5b
Frost Dates for 61341 — Marseilles, Illinois
Averages from Marseilles Lock, Il US, the nearest reporting station, 3 miles away.
Plant tender crops after April 27, and expect the first autumn freeze around October 17. That leaves about 171 frost-free days.
- Last spring frost
- April 27
- First fall frost
- October 17
- Growing season
- 171 days
- Hardiness zone
- 5b
50% probability
50% probability
frost-free
-15 to -10°F annual low
- First snow
- December 2
- Last snow
- March 18
- Winters with snow
- 96%
- Snow per year
- 25"
median, 1991–2020
median, 1991–2020
26 of 27 observed
NOAA normal
When it snows in Marseilles, Illinois
The first measurable snow (0.1 inch or more) in Marseilles, Illinois usually arrives around December 2, and the last of the season around March 18. Those are the middle dates across the winters of 1991–2020 at Marseilles Lock, Il US: half of years saw snow earlier, half later. Snow fell in 96% of those winters.
For a gardener, snow matters less than frost: a light snow on frozen ground changes nothing, while a hard frost on an unprotected bed ends the season. Use the frost dates above for planting and the snow dates for getting hoses drained, mulch down and tender pots indoors.
Planting calendar for 61341
| When | What to do |
|---|---|
| February 16 – March 2 | Start peppers and aubergines indoors They need eight to ten weeks under lights before they can go out. |
| March 2 – March 16 | Start tomatoes indoors Six to eight weeks gives a transplant big enough to set fruit early. |
| March 30 – April 13 | Sow peas, spinach, lettuce, radish outdoors These tolerate light frost and prefer to germinate in cool soil. |
| April 27 onward | Transplant tomatoes, peppers, basil, squash, cucumbers The average last freeze has passed — still watch the actual forecast. |
| by July 25 | Sow the autumn crop of carrots, beets and brassicas They need about twelve weeks to size up before growth stops. |
| by October 3 | Harvest tender crops, or be ready to cover them A first freeze two weeks early is well within normal variation. |
| October 17 onward | Plant garlic, mulch beds, lift tender bulbs Garlic wants a cold spell; bare soil loses structure over winter. |
What these dates mean
Wait until after April 27 to put tender plants — tomatoes, peppers, basil, squash — in the ground. That is the date by which half of years in Marseilles, Illinois are past their last freeze. Harvest before October 17, which leaves roughly 171 frost-free days.
ZIP 61341 sits in USDA hardiness zone 5b, meaning the average coldest night of the year falls between -15 to -10°F. Zone decides what survives the winter; frost dates decide when to plant each spring. They are different questions, and a plant can pass one and fail the other.
These are thirty-year NOAA averages for 1991–2020, not a forecast. Any individual year can frost two to three weeks either side of these dates, so check the actual forecast before planting out.