USDA Hardiness Zone 5b
Frost Dates for 61270 — Morrison, Illinois
NOAA 1991–2020 normals from Morrison, IL (632 ft), 2 miles south.
Updated
In Morrison, the last spring frost (32°F) is around April 26 in half of years and has passed by May 11 in nine years out of ten. The first fall frost comes around October 13, as early as September 30 one year in ten, leaving a typical freeze-free season of 167 days (NOAA, Morrison, IL).
- Last spring frost
- April 26
- First fall frost
- October 13
- Growing season
- 167 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 25
- Last snow
- March 17
- Winters with snow
- 100%
- Snow per year
- 31.5"
median, 1991–2020
median, 1991–2020
28 of 28 observed
NOAA normal
Frost risk by date in Morrison
Half of springs at Morrison, IL see their last 32°F night by April 26; only one in ten is past it by April 13, and one in ten still has one after May 11. Planting tender crops after May 2 leaves a 30% risk of a frost on them, after May 6 20%, and after May 11 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 13 in half of years, as early as September 30 one year in ten, and holds off past October 25 one year in ten. A hard freeze of 28°F follows 10 days later, around October 23; in spring the one-in-ten date for 28°F is April 30, 11 days before the 32°F one. The freeze-free season lasts 167 days in a typical year, shorter than at 92% of the 158 Illinois stations; it reaches 188 days one year in ten and falls short of 150 one year in ten. On average 145 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 6, and return around October 3. Severe cold of 16°F or below comes every winter, usually between November 23 and March 13.
| Low | 90% | 80% | 70% | 60% | 50% | 40% | 30% | 20% | 10% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Apr 23 | Apr 27 | Apr 30 | May 3 | May 6 | May 9 | May 13 | May 17 | May 22 |
| 32°F | Apr 13 | Apr 17 | Apr 20 | Apr 23 | Apr 26 | Apr 29 | May 2 | May 6 | May 11 |
| 28°F | Apr 2 | Apr 5 | Apr 8 | Apr 11 | Apr 15 | Apr 17 | Apr 20 | Apr 24 | Apr 30 |
| 24°F | Mar 16 | Mar 23 | Mar 30 | Apr 1 | Apr 3 | Apr 5 | Apr 9 | Apr 13 | Apr 18 |
| 20°F | Mar 7 | Mar 12 | Mar 16 | Mar 20 | Mar 23 | Mar 28 | Mar 31 | Apr 2 | Apr 8 |
| 16°F | Feb 28 | Mar 4 | Mar 7 | Mar 10 | Mar 13 | Mar 16 | Mar 19 | Mar 23 | Mar 29 |
| Low | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Sep 20 | Sep 25 | Sep 28 | Oct 1 | Oct 3 | Oct 6 | Oct 8 | Oct 11 | Oct 15 |
| 32°F | Sep 30 | Oct 5 | Oct 9 | Oct 11 | Oct 13 | Oct 15 | Oct 18 | Oct 21 | Oct 25 |
| 28°F | Oct 11 | Oct 15 | Oct 19 | Oct 21 | Oct 23 | Oct 25 | Oct 28 | Oct 30 | Nov 3 |
| 24°F | Oct 21 | Oct 25 | Oct 28 | Oct 31 | Nov 1 | Nov 4 | Nov 7 | Nov 11 | Nov 16 |
| 20°F | Nov 1 | Nov 3 | Nov 7 | Nov 10 | Nov 13 | Nov 16 | Nov 19 | Nov 23 | Nov 28 |
| 16°F | Nov 8 | Nov 13 | Nov 17 | Nov 20 | Nov 23 | Nov 25 | Nov 28 | Dec 1 | Dec 7 |
Freeze probabilities 1991–2020 at Morrison, 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 61270 →Compare Morrison with another place →
Weather by month in Morrison
July is the warmest month at Morrison, IL, averaging 83°F by day and 62°F at night; January is the coldest at 29°F and 12°F. A freezing night is all but certain in every month from October to April (a 90% chance or more). From June to August the chance of a 32°F night stays under 10% each month. In spring, May still brings one in 36% of years.
Warmth for growing adds up to 2,876 growing degree days a year (base 50°F), fewer than at 90% of the 158 Illinois stations. 35% of them (1,002) have built up by the end of June, and July adds the most, 699. Precipitation totals 38.3 inches a year, most in June (4.9") and least in January (1.5"); May to September bring 56% of it.
| Month | High °F | Low °F | Precip. in | 32°F night | Nights ≤ 32°F | GDD 50°F |
|---|---|---|---|---|---|---|
| Jan | 29 | 12 | 1.5 | 100% | 30 | 0 |
| Feb | 34 | 16 | 1.7 | 100% | 26 | 1 |
| Mar | 46 | 27 | 2.5 | 100% | 23 | 19 |
| Apr | 60 | 37 | 3.8 | 99% | 9 | 86 |
| May | 71 | 49 | 4.7 | 36% | 1 | 319 |
| Jun | 80 | 59 | 4.9 | 0% | 0 | 578 |
| Jul | 83 | 62 | 4.2 | 0% | 0 | 699 |
| Aug | 81 | 60 | 4.3 | 0% | 0 | 632 |
| Sep | 75 | 51 | 3.4 | 11% | 1 | 398 |
| Oct | 62 | 39 | 2.8 | 97% | 8 | 127 |
| Nov | 47 | 28 | 2.5 | 100% | 20 | 16 |
| Dec | 35 | 18 | 2.0 | 100% | 29 | 2 |
Monthly normals 1991–2020 at Morrison, IL (632 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, Fulton L&D #13, IL, 11 miles northwest of Morrison, has a last frost 13 days earlier (April 13), a first frost 13 days later (October 26), a season 28 days longer.
When it snows in Morrison, Illinois
The first measurable snow (0.1 inch or more) in Morrison usually arrives around November 25, and the last of the season around March 17. Those are the middle dates across the winters of 1991–2020 at Morrison, IL, 1.7 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 40 days after the last snow.
Planting calendar for 61270
| 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 21 | Sow the autumn crop of carrots, beets and brassicasThey need about twelve weeks to size up before growth stops. |
| by September 29 | Harvest tender crops, or be ready to cover themA first freeze two weeks early is well within normal variation. |
| October 13 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 61270 is 2 miles from Morrison, IL, which stands at 632 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 2 other ZIP codes share the station. The 2023 USDA Plant Hardiness Zone Map lists ZIP 61270 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.