USDA Hardiness Zone 5b
Frost Dates for 61354 — Peru, Illinois
NOAA 1991–2020 normals from Peru, IL (620 ft), 2 miles northeast.
Updated
In Peru, the last spring frost (32°F) is around April 24 in half of years and has passed by May 8 in nine years out of ten. The first fall frost comes around October 18, as early as October 3 one year in ten, leaving a typical freeze-free season of 176 days (NOAA, Peru, IL).
- Last spring frost
- April 24
- First fall frost
- October 18
- Growing season
- 176 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
- November 26
- Last snow
- March 22
- Winters with snow
- 100%
- Snow per year
- 28.5"
median, 1991–2020
median, 1991–2020
20 of 20 observed
NOAA normal
Frost risk by date in Peru
Half of springs at Peru, IL see their last 32°F night by April 24; only one in ten is past it by April 11, and one in ten still has one after May 8. Planting tender crops after April 30 leaves a 30% risk of a frost on them, after May 3 20%, and after May 8 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 18 in half of years, as early as October 3 one year in ten, and holds off past October 28 one year in ten. A hard freeze of 28°F follows 10 days later, around October 28; in spring the one-in-ten date for 28°F is April 27, 11 days before the 32°F one. The freeze-free season lasts 176 days in a typical year, shorter than at 73% of the 158 Illinois stations; it reaches 194 days one year in ten and falls short of 154 one year in ten. On average 139 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 10 days longer, to about May 4, 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 25 | Apr 29 | May 1 | May 4 | May 6 | May 9 | May 14 | May 19 |
| 32°F | Apr 11 | Apr 16 | Apr 19 | Apr 21 | Apr 24 | Apr 26 | Apr 30 | May 3 | May 8 |
| 28°F | Mar 31 | Apr 4 | Apr 7 | Apr 10 | Apr 13 | Apr 16 | Apr 19 | Apr 22 | Apr 27 |
| 24°F | Mar 17 | Mar 23 | Mar 28 | Mar 31 | Apr 2 | Apr 4 | Apr 7 | Apr 11 | Apr 17 |
| 20°F | Mar 6 | Mar 12 | Mar 15 | Mar 19 | Mar 22 | Mar 26 | Mar 30 | Apr 1 | Apr 7 |
| 16°F | Feb 27 | Mar 3 | Mar 6 | Mar 9 | Mar 13 | Mar 15 | Mar 18 | Mar 23 | Mar 28 |
| Low | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Sep 23 | Sep 28 | Oct 1 | Oct 4 | Oct 6 | Oct 10 | Oct 12 | Oct 16 | Oct 20 |
| 32°F | Oct 3 | Oct 9 | Oct 12 | Oct 15 | Oct 18 | Oct 20 | Oct 22 | Oct 25 | Oct 28 |
| 28°F | Oct 16 | Oct 21 | Oct 23 | Oct 25 | Oct 28 | Oct 30 | Nov 1 | Nov 3 | Nov 8 |
| 24°F | Oct 28 | Oct 31 | Nov 1 | Nov 4 | Nov 7 | Nov 10 | Nov 13 | Nov 16 | Nov 21 |
| 20°F | Nov 4 | Nov 8 | Nov 12 | Nov 15 | Nov 18 | Nov 21 | Nov 24 | Nov 29 | Dec 3 |
| 16°F | Nov 11 | Nov 16 | Nov 20 | Nov 23 | Nov 26 | Nov 30 | Dec 3 | Dec 7 | Dec 15 |
Freeze probabilities 1991–2020 at Peru, 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 61354 →Compare Peru with another place →
Weather by month in Peru
July is the warmest month at Peru, IL, averaging 84°F by day and 63°F at night; January is the coldest at 30°F and 14°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 26% of years.
Warmth for growing adds up to 3,121 growing degree days a year (base 50°F), fewer than at 76% of the 158 Illinois stations. 35% of them (1,094) have built up by the end of June, and July adds the most, 725. Precipitation totals 38.1 inches a year, most in June (4.6") and least in January (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 | 30 | 14 | 1.8 | 100% | 29 | 1 |
| Feb | 35 | 18 | 1.8 | 100% | 26 | 1 |
| Mar | 48 | 27 | 2.3 | 100% | 23 | 26 |
| Apr | 61 | 38 | 3.8 | 99% | 8 | 107 |
| May | 73 | 49 | 4.5 | 26% | 1 | 349 |
| Jun | 81 | 59 | 4.6 | 0% | 0 | 611 |
| Jul | 84 | 63 | 3.9 | 0% | 0 | 725 |
| Aug | 82 | 61 | 3.7 | 0% | 0 | 666 |
| Sep | 77 | 53 | 3.4 | 8% | <1 | 446 |
| Oct | 64 | 41 | 3.5 | 94% | 6 | 162 |
| Nov | 48 | 30 | 2.7 | 100% | 19 | 26 |
| Dec | 36 | 20 | 2.1 | 100% | 28 | 2 |
Monthly normals 1991–2020 at Peru, IL (620 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, Ottawa 5SW, IL, 11 miles east of Peru, has a last frost 4 days earlier (April 20), a first frost 4 days later (October 22), a season 7 days longer.
When it snows in Peru, Illinois
The first measurable snow (0.1 inch or more) in Peru usually arrives around November 26, and the last of the season around March 22. Those are the middle dates across the winters of 1991–2020 at Peru, IL, 1.8 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 33 days after the last snow.
Planting calendar for 61354
| When | What to do |
|---|---|
| February 13 – February 27 | Start peppers and aubergines indoorsThey need eight to ten weeks under lights before they can go out. |
| February 27 – March 13 | Start tomatoes indoorsSix to eight weeks gives a transplant big enough to set fruit early. |
| March 27 – April 10 | Sow peas, spinach, lettuce, radish outdoorsThese tolerate light frost and prefer to germinate in cool soil. |
| April 24 onward | Transplant tomatoes, peppers, basil, squash, cucumbersThe average last freeze has passed — still watch the actual forecast. |
| by July 26 | Sow the autumn crop of carrots, beets and brassicasThey need about twelve weeks to size up before growth stops. |
| by October 4 | Harvest tender crops, or be ready to cover themA first freeze two weeks early is well within normal variation. |
| October 18 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 61354 is 2 miles from Peru, IL, which stands at 620 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 4 other ZIP codes share the station. The 2023 USDA Plant Hardiness Zone Map lists ZIP 61354 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.