USDA Hardiness Zone 6a
Frost Dates for 61873 — Saint Joseph, Illinois
NOAA 1991–2020 normals from Ogden, IL (675 ft), 4 miles east.
Updated
In Saint Joseph, the last spring frost (32°F) is around April 20 in half of years and has passed by May 7 in nine years out of ten. The first fall frost comes around October 21, as early as October 8 one year in ten, leaving a typical freeze-free season of 182 days (NOAA, Ogden, IL).
- Last spring frost
- April 20
- First fall frost
- October 21
- Growing season
- 182 days
- Hardiness zone
- 6a
50% probability
50% probability
freeze-free, 50%
-10 to -5°F (-23.3 to -20.6°C) coldest night
- First snow
- November 25
- Last snow
- March 19
- Winters with snow
- 100%
- Snow per year
- 25"
median, 1991–2020
median, 1991–2020
19 of 19 observed
NOAA normal
Frost risk by date in Saint Joseph
Half of springs at Ogden, IL see their last 32°F night by April 20; only one in ten is past it by April 7, and one in ten still has one after May 7. Planting tender crops after April 26 leaves a 30% risk of a frost on them, after May 1 20%, and after May 7 10%. The 17 days between the even-odds date and the one-in-ten date is wider than at 79% of the 158 Illinois stations behind this site's ZIP pages.
In fall the first 32°F night comes by October 21 in half of years, as early as October 8 one year in ten, and holds off past November 2 one year in ten. A hard freeze of 28°F follows 10 days later, around October 31; in spring the one-in-ten date for 28°F is April 25, 12 days before the 32°F one. The freeze-free season lasts 182 days in a typical year, shorter than at 56% of the 158 Illinois stations; it reaches 200 days one year in ten and falls short of 160 one year in ten. On average 118 nights a year drop to 32°F or below. Nights of 36°F, when frost can still settle on leaves in low, open spots, continue 12 days longer, to about May 2, and return around October 12. Severe cold of 16°F or below comes every winter, usually between November 29 and March 11.
| Low | 90% | 80% | 70% | 60% | 50% | 40% | 30% | 20% | 10% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Apr 18 | Apr 22 | Apr 25 | Apr 28 | May 2 | May 5 | May 8 | May 12 | May 16 |
| 32°F | Apr 7 | Apr 12 | Apr 15 | Apr 18 | Apr 20 | Apr 23 | Apr 26 | May 1 | May 7 |
| 28°F | Mar 29 | Apr 2 | Apr 5 | Apr 7 | Apr 9 | Apr 12 | Apr 15 | Apr 19 | Apr 25 |
| 24°F | Mar 14 | Mar 21 | Mar 24 | Mar 28 | Mar 31 | Apr 2 | Apr 4 | Apr 7 | Apr 14 |
| 20°F | Mar 4 | Mar 9 | Mar 13 | Mar 17 | Mar 20 | Mar 23 | Mar 27 | Mar 30 | Apr 3 |
| 16°F | Feb 23 | Mar 1 | Mar 5 | Mar 8 | Mar 11 | Mar 15 | Mar 17 | Mar 21 | Mar 27 |
| Low | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Sep 27 | Oct 1 | Oct 6 | Oct 9 | Oct 12 | Oct 15 | Oct 17 | Oct 20 | Oct 23 |
| 32°F | Oct 8 | Oct 13 | Oct 16 | Oct 19 | Oct 21 | Oct 24 | Oct 26 | Oct 29 | Nov 2 |
| 28°F | Oct 19 | Oct 23 | Oct 26 | Oct 29 | Oct 31 | Nov 1 | Nov 5 | Nov 9 | Nov 14 |
| 24°F | Oct 30 | Nov 1 | Nov 5 | Nov 7 | Nov 11 | Nov 13 | Nov 17 | Nov 21 | Nov 26 |
| 20°F | Nov 5 | Nov 10 | Nov 13 | Nov 17 | Nov 20 | Nov 23 | Nov 27 | Dec 1 | Dec 7 |
| 16°F | Nov 11 | Nov 17 | Nov 22 | Nov 26 | Nov 29 | Dec 3 | Dec 7 | Dec 13 | Dec 19 |
Freeze probabilities 1991–2020 at Ogden, IL, from NOAA NCEI U.S. Climate Normals. Where a temperature is reached in fewer than 99.5% of years, the dates describe only the years that reach it. Not a forecast.
Frost risk on any date in 61873 →Compare Saint Joseph with another place →
Compared with the next station
The nearest other station, Champaign 3S, IL, 11 miles west of Saint Joseph, has a last frost 5 days earlier (April 15), a first frost 3 days later (October 24), a season 8 days longer.
When it snows in Saint Joseph, Illinois
The first measurable snow (0.1 inch or more) in Saint Joseph usually arrives around November 25, and the last of the season around March 19. Those are the middle dates across the winters of 1991–2020 at Ogden, IL, 4.2 miles away: half of years saw snow earlier, half later. Every one of those winters saw snow. The last 32°F night of spring typically comes 32 days after the last snow.
Planting calendar for 61873
| When | What to do |
|---|---|
| February 9 – February 23 | Start peppers and aubergines indoorsThey need eight to ten weeks under lights before they can go out. |
| February 23 – March 9 | Start tomatoes indoorsSix to eight weeks gives a transplant big enough to set fruit early. |
| March 23 – April 6 | Sow peas, spinach, lettuce, radish outdoorsThese tolerate light frost and prefer to germinate in cool soil. |
| April 20 onward | Transplant tomatoes, peppers, basil, squash, cucumbersThe average last freeze has passed — still watch the actual forecast. |
| by July 29 | Sow the autumn crop of carrots, beets and brassicasThey need about twelve weeks to size up before growth stops. |
| by October 7 | Harvest tender crops, or be ready to cover themA first freeze two weeks early is well within normal variation. |
| October 21 onward | Plant garlic, mulch beds, lift tender bulbsGarlic wants a cold spell; bare soil loses structure over winter. |
The weeks before and after the 50% dates are general rules of thumb, not NOAA figures; a seed packet gives the timing for each variety.
Where these figures come from
ZIP 61873 is 4 miles from Ogden, IL, which stands at 675 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. The 2023 USDA Plant Hardiness Zone Map lists ZIP 61873 in zone 6a, the band where the coldest night of the year averaged -10 to -5°F (-23.3 to -20.6°C) over 1991–2020; a zone describes winter lows, not frost dates.
Hardiness zone and temperature range: USDA Plant Hardiness Zone Map 2023 (USDA-ARS, Oregon State University), ZIP-code listing, unchanged. °C converted from °F by this site.
Thirty-year averages, not a forecast: check the forecast before planting out. How stations are matched and which pages are offered to search engines: methodology.