USDA Hardiness Zone 6a
Frost Dates for 62675 — Petersburg, Illinois
NOAA 1991–2020 normals from Petersburg 1E, IL (600 ft), 1 miles northeast.
Updated
In Petersburg, the last spring frost (32°F) is around April 13 in half of years and has passed by April 28 in nine years out of ten. The first fall frost comes around October 21, as early as October 7 one year in ten, leaving a typical freeze-free season of 189 days (NOAA, Petersburg 1E, IL).
- Last spring frost
- April 13
- First fall frost
- October 21
- Growing season
- 189 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
- December 1
- Last snow
- March 15
- Winters with snow
- 100%
- Snow per year
- 15.2"
median, 1991–2020
median, 1991–2020
22 of 22 observed
NOAA normal
Frost risk by date in Petersburg
Half of springs at Petersburg 1E, IL see their last 32°F night by April 13; only one in ten is past it by March 31, and one in ten still has one after April 28. Planting tender crops after April 18 leaves a 30% risk of a frost on them, after April 22 20%, and after April 28 10%. The 15 days between the even-odds date and the one-in-ten date is narrower than at 54% 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 7 one year in ten, and holds off past November 3 one year in ten. A hard freeze of 28°F follows 11 days later, around November 1; in spring the one-in-ten date for 28°F is April 17, 11 days before the 32°F one. The freeze-free season lasts 189 days in a typical year, longer than at 62% of the 158 Illinois stations; it reaches 209 days one year in ten and falls short of 170 one year in ten. On average 121 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 11 days longer, to about April 24, and return around October 12. Severe cold of 16°F or below comes every winter, usually between December 1 and March 8.
| Low | 90% | 80% | 70% | 60% | 50% | 40% | 30% | 20% | 10% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Apr 10 | Apr 15 | Apr 18 | Apr 21 | Apr 24 | Apr 27 | Apr 30 | May 2 | May 8 |
| 32°F | Mar 31 | Apr 4 | Apr 7 | Apr 9 | Apr 13 | Apr 15 | Apr 18 | Apr 22 | Apr 28 |
| 28°F | Mar 18 | Mar 24 | Mar 29 | Apr 1 | Apr 3 | Apr 5 | Apr 7 | Apr 10 | Apr 17 |
| 24°F | Mar 9 | Mar 14 | Mar 18 | Mar 21 | Mar 24 | Mar 28 | Mar 31 | Apr 3 | Apr 7 |
| 20°F | Feb 28 | Mar 5 | Mar 10 | Mar 13 | Mar 16 | Mar 19 | Mar 22 | Mar 26 | Mar 31 |
| 16°F | Feb 15 | Feb 25 | Mar 1 | Mar 4 | Mar 8 | Mar 11 | Mar 14 | Mar 18 | Mar 22 |
| Low | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Sep 29 | Oct 3 | Oct 6 | Oct 9 | Oct 12 | Oct 14 | Oct 17 | Oct 19 | Oct 23 |
| 32°F | Oct 7 | Oct 13 | Oct 16 | Oct 19 | Oct 21 | Oct 23 | Oct 25 | Oct 29 | Nov 3 |
| 28°F | Oct 19 | Oct 24 | Oct 26 | Oct 29 | Nov 1 | Nov 3 | Nov 6 | Nov 9 | Nov 14 |
| 24°F | Oct 28 | Nov 1 | Nov 4 | Nov 7 | Nov 11 | Nov 14 | Nov 18 | Nov 22 | Nov 28 |
| 20°F | Nov 7 | Nov 11 | Nov 14 | Nov 18 | Nov 21 | Nov 26 | Nov 29 | Dec 2 | Dec 9 |
| 16°F | Nov 13 | Nov 19 | Nov 24 | Nov 27 | Dec 1 | Dec 4 | Dec 8 | Dec 14 | Dec 20 |
Freeze probabilities 1991–2020 at Petersburg 1E, 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 62675 →Compare Petersburg with another place →
Compared with the next station
The nearest other station, Athens 4SW, IL, 6 miles southeast of Petersburg, has a last frost 6 days later (April 19), a first frost 2 days earlier (October 19), a season 8 days shorter.
When it snows in Petersburg, Illinois
The first measurable snow (0.1 inch or more) in Petersburg usually arrives around December 1, and the last of the season around March 15. Those are the middle dates across the winters of 1991–2020 at Petersburg 1E, IL, 1 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 29 days after the last snow.
Planting calendar for 62675
| When | What to do |
|---|---|
| February 2 – February 16 | Start peppers and aubergines indoorsThey need eight to ten weeks under lights before they can go out. |
| February 16 – March 2 | Start tomatoes indoorsSix to eight weeks gives a transplant big enough to set fruit early. |
| March 16 – March 30 | Sow peas, spinach, lettuce, radish outdoorsThese tolerate light frost and prefer to germinate in cool soil. |
| April 13 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 62675 is 1 mile from Petersburg 1E, IL, which stands at 600 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. The 2023 USDA Plant Hardiness Zone Map lists ZIP 62675 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.