USDA Hardiness Zone 5b
Frost Dates for 61561 — Roanoke, Illinois
NOAA 1991–2020 normals from Minonk, IL (750 ft), 12 miles northeast.
Updated
In Roanoke, the last spring frost (32°F) is around April 26 in half of years and has passed by May 10 in nine years out of ten. The first fall frost comes around October 17, as early as October 1 one year in ten, leaving a typical freeze-free season of 173 days (NOAA, Minonk, IL).
- Last spring frost
- April 26
- First fall frost
- October 17
- Growing season
- 173 days
- Hardiness zone
- 5b
50% probability
50% probability
freeze-free, 50%
-15 to -10°F (-26.1 to -23.3°C) coldest night
- First snow
- December 1
- Last snow
- March 4
- Winters with snow
- 100%
- Snow per year
- 21.2"
median, 1991–2020
median, 1991–2020
15 of 15 observed
NOAA normal
Frost risk by date in Roanoke
Half of springs at Minonk, IL see their last 32°F night by April 26; only one in ten is past it by April 11, and one in ten still has one after May 10. Planting tender crops after May 1 leaves a 30% risk of a frost on them, after May 5 20%, and after May 10 10%. The 14 days between the even-odds date and the one-in-ten date is narrower than at 82% of the 158 Illinois stations behind this site's ZIP pages.
In fall the first 32°F night comes by October 17 in half of years, as early as October 1 one year in ten, and holds off past October 29 one year in ten. A hard freeze of 28°F follows 11 days later, around October 28; in spring the one-in-ten date for 28°F is May 1, 9 days before the 32°F one. The freeze-free season lasts 173 days in a typical year, shorter than at 81% of the 158 Illinois stations; it reaches 193 days one year in ten and falls short of 152 one year in ten. On average 135 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 9 days longer, to about May 5, and return around October 6. Severe cold of 16°F or below comes every winter, usually between November 26 and March 13.
| Low | 90% | 80% | 70% | 60% | 50% | 40% | 30% | 20% | 10% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Apr 21 | Apr 26 | Apr 29 | May 2 | May 5 | May 7 | May 11 | May 15 | May 20 |
| 32°F | Apr 11 | Apr 16 | Apr 20 | Apr 23 | Apr 26 | Apr 29 | May 1 | May 5 | May 10 |
| 28°F | Apr 1 | Apr 5 | Apr 8 | Apr 12 | Apr 15 | Apr 18 | Apr 22 | Apr 26 | May 1 |
| 24°F | Mar 18 | Mar 24 | Mar 29 | Apr 1 | Apr 4 | Apr 6 | Apr 9 | Apr 15 | Apr 21 |
| 20°F | Mar 8 | Mar 13 | Mar 17 | Mar 20 | Mar 24 | Mar 28 | Mar 31 | Apr 3 | Apr 9 |
| 16°F | Feb 25 | Mar 3 | Mar 7 | Mar 10 | Mar 13 | Mar 16 | Mar 20 | Mar 25 | Mar 31 |
| Low | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Sep 23 | Sep 27 | Oct 1 | Oct 4 | Oct 6 | Oct 9 | Oct 12 | Oct 15 | Oct 20 |
| 32°F | Oct 1 | Oct 7 | Oct 12 | Oct 14 | Oct 17 | Oct 20 | Oct 22 | Oct 25 | Oct 29 |
| 28°F | Oct 14 | Oct 19 | Oct 22 | Oct 25 | Oct 28 | Oct 30 | Nov 1 | Nov 3 | Nov 9 |
| 24°F | Oct 25 | Oct 30 | Nov 1 | Nov 3 | Nov 6 | Nov 9 | Nov 12 | Nov 16 | Nov 21 |
| 20°F | Nov 2 | Nov 7 | Nov 10 | Nov 13 | Nov 17 | Nov 19 | Nov 23 | Nov 27 | Dec 4 |
| 16°F | Nov 10 | Nov 15 | Nov 19 | Nov 22 | Nov 26 | Nov 30 | Dec 3 | Dec 7 | Dec 14 |
Freeze probabilities 1991–2020 at Minonk, 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 61561 →Compare Roanoke with another place →
Weather by month in Roanoke
July is the warmest month at Minonk, IL, averaging 86°F by day and 64°F at night; January is the coldest at 33°F and 15°F. A freezing night is all but certain in every month from October to April (a 90% chance or more). From June to September the chance of a 32°F night stays under 10% each month. In spring, May still brings one in 32% of years.
Warmth for growing adds up to 3,432 growing degree days a year (base 50°F), fewer than at 55% of the 158 Illinois stations. 36% of them (1,220) have built up by the end of June, and July adds the most, 775. Precipitation totals 37.7 inches a year, most in May (4.6") and least in February (1.8"); May to September bring 53% of it.
| Month | High °F | Low °F | Precip. in | 32°F night | Nights ≤ 32°F | GDD 50°F |
|---|---|---|---|---|---|---|
| Jan | 33 | 15 | 2.0 | 100% | 29 | 1 |
| Feb | 38 | 19 | 1.8 | 100% | 26 | 3 |
| Mar | 50 | 29 | 2.5 | 100% | 22 | 34 |
| Apr | 63 | 39 | 3.7 | 99% | 8 | 131 |
| May | 74 | 51 | 4.6 | 32% | 1 | 396 |
| Jun | 83 | 61 | 4.0 | 0% | 0 | 655 |
| Jul | 86 | 64 | 3.8 | 0% | 0 | 775 |
| Aug | 84 | 62 | 3.5 | 0% | 0 | 713 |
| Sep | 79 | 54 | 3.9 | 8% | <1 | 493 |
| Oct | 66 | 42 | 3.1 | 93% | 5 | 192 |
| Nov | 51 | 31 | 2.6 | 100% | 18 | 36 |
| Dec | 38 | 21 | 2.2 | 100% | 27 | 3 |
Monthly normals 1991–2020 at Minonk, IL (750 ft), NOAA NCEI. "32°F night": chance of at least one in the month. GDD: growing degree days, base 50°F.
Compared with the next station
The nearest other station, Congerville 2NW, IL, 12 miles south of Roanoke, has a last frost 5 days earlier (April 21), the same first-frost date, a season 5 days longer.
When it snows in Roanoke, Illinois
The first measurable snow (0.1 inch or more) in Roanoke usually arrives around December 1, and the last of the season around March 4. Those are the middle dates across the winters of 1991–2020 at Eureka, IL, 6.8 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 53 days after the last snow.
Planting calendar for 61561
| When | What to do |
|---|---|
| February 15 – March 1 | Start peppers and aubergines indoorsThey need eight to ten weeks under lights before they can go out. |
| March 1 – March 15 | Start tomatoes indoorsSix to eight weeks gives a transplant big enough to set fruit early. |
| March 29 – April 12 | Sow peas, spinach, lettuce, radish outdoorsThese tolerate light frost and prefer to germinate in cool soil. |
| April 26 onward | Transplant tomatoes, peppers, basil, squash, cucumbersThe average last freeze has passed — still watch the actual forecast. |
| by July 25 | Sow the autumn crop of carrots, beets and brassicasThey need about twelve weeks to size up before growth stops. |
| by October 3 | Harvest tender crops, or be ready to cover themA first freeze two weeks early is well within normal variation. |
| October 17 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 61561 is 12 miles from Minonk, IL, which stands at 750 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 2 other ZIP codes share the station; its figures are presented in full for 61738 (El Paso). The 2023 USDA Plant Hardiness Zone Map lists ZIP 61561 in zone 5b, the band where the coldest night of the year averaged -15 to -10°F (-26.1 to -23.3°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.