USDA Hardiness Zone 5b
Frost Dates for 61275 — Port Byron, Illinois
NOAA 1991–2020 normals from Le Claire L&D 14, IA (577 ft), 5 miles west.
Updated
In Port Byron, the last spring frost (32°F) is around April 16 in half of years and has passed by April 30 in nine years out of ten. The first fall frost comes around October 25, as early as October 11 one year in ten, leaving a typical freeze-free season of 190 days (NOAA, Le Claire L&D 14, IA).
- Last spring frost
- April 16
- First fall frost
- October 25
- Growing season
- 190 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 17
- Winters with snow
- 100%
- Snow per year
- 28.4"
median, 1991–2020
median, 1991–2020
28 of 28 observed
NOAA normal
Frost risk by date in Port Byron
Half of springs at Le Claire L&D 14, IA see their last 32°F night by April 16; only one in ten is past it by April 2, and one in ten still has one after April 30. Planting tender crops after April 22 leaves a 30% risk of a frost on them, after April 25 20%, and after April 30 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 25 in half of years, as early as October 11 one year in ten, and holds off past November 6 one year in ten. A hard freeze of 28°F follows 8 days later, around November 2; in spring the one-in-ten date for 28°F is April 21, 9 days before the 32°F one. The freeze-free season lasts 190 days in a typical year, longer than at 66% of the 158 Illinois stations; it reaches 209 days one year in ten and falls short of 172 one year in ten. On average 126 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 27, and return around October 15. Severe cold of 16°F or below comes every winter, usually between December 1 and March 10.
| Low | 90% | 80% | 70% | 60% | 50% | 40% | 30% | 20% | 10% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Apr 11 | Apr 17 | Apr 20 | Apr 23 | Apr 27 | Apr 30 | May 2 | May 5 | May 8 |
| 32°F | Apr 2 | Apr 6 | Apr 9 | Apr 13 | Apr 16 | Apr 18 | Apr 22 | Apr 25 | Apr 30 |
| 28°F | Mar 21 | Mar 27 | Apr 1 | Apr 3 | Apr 6 | Apr 8 | Apr 11 | Apr 15 | Apr 21 |
| 24°F | Mar 10 | Mar 15 | Mar 19 | Mar 23 | Mar 27 | Mar 31 | Apr 2 | Apr 5 | Apr 9 |
| 20°F | Mar 3 | Mar 7 | Mar 11 | Mar 14 | Mar 17 | Mar 21 | Mar 24 | Mar 29 | Apr 2 |
| 16°F | Feb 24 | Mar 1 | Mar 4 | Mar 7 | Mar 10 | Mar 13 | Mar 15 | Mar 20 | Mar 26 |
| Low | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Oct 1 | Oct 6 | Oct 10 | Oct 12 | Oct 15 | Oct 18 | Oct 20 | Oct 24 | Oct 28 |
| 32°F | Oct 11 | Oct 16 | Oct 20 | Oct 22 | Oct 25 | Oct 28 | Oct 30 | Nov 1 | Nov 6 |
| 28°F | Oct 23 | Oct 27 | Oct 30 | Nov 1 | Nov 2 | Nov 5 | Nov 8 | Nov 13 | Nov 18 |
| 24°F | Nov 1 | Nov 4 | Nov 7 | Nov 10 | Nov 13 | Nov 16 | Nov 19 | Nov 23 | Nov 29 |
| 20°F | Nov 7 | Nov 12 | Nov 16 | Nov 19 | Nov 22 | Nov 26 | Nov 30 | Dec 2 | Dec 8 |
| 16°F | Nov 13 | Nov 18 | Nov 23 | Nov 27 | Dec 1 | Dec 2 | Dec 6 | Dec 9 | Dec 16 |
Freeze probabilities 1991–2020 at Le Claire L&D 14, IA, 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 61275 →Compare Port Byron with another place →
Weather by month in Port Byron
July is the warmest month at Le Claire L&D 14, IA, averaging 85°F by day and 66°F at night; January is the coldest at 31°F and 14°F. A freezing night is all but certain in every month from November to April (a 90% chance or more). From May to September the chance of a 32°F night stays under 10% each month.
Warmth for growing adds up to 3,395 growing degree days a year (base 50°F), fewer than at 57% of the 158 Illinois stations. 34% of them (1,170) have built up by the end of June, and July adds the most, 792. Precipitation totals 37.2 inches a year, most in May (4.8") and least in January (1.5"); May to September bring 57% of it.
| Month | High °F | Low °F | Precip. in | 32°F night | Nights ≤ 32°F | GDD 50°F |
|---|---|---|---|---|---|---|
| Jan | 31 | 14 | 1.5 | 100% | 29 | 0 |
| Feb | 35 | 18 | 1.6 | 100% | 25 | 1 |
| Mar | 47 | 28 | 2.6 | 100% | 21 | 23 |
| Apr | 61 | 40 | 3.8 | 93% | 5 | 114 |
| May | 72 | 52 | 4.8 | 8% | 0 | 375 |
| Jun | 82 | 62 | 4.6 | 0% | 0 | 657 |
| Jul | 85 | 66 | 4.2 | 0% | 0 | 792 |
| Aug | 83 | 64 | 4.1 | 0% | 0 | 730 |
| Sep | 77 | 56 | 3.4 | 0% | 0 | 491 |
| Oct | 64 | 44 | 2.6 | 74% | 3 | 184 |
| Nov | 48 | 31 | 2.1 | 100% | 16 | 26 |
| Dec | 36 | 21 | 1.9 | 100% | 27 | 2 |
Monthly normals 1991–2020 at Le Claire L&D 14, IA (577 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, Davenport WFO, IA, 13 miles west of Port Byron and 173 feet higher, has a last frost 5 days later (April 21), a first frost 8 days earlier (October 17), a season 14 days shorter.
When it snows in Port Byron, Illinois
The first measurable snow (0.1 inch or more) in Port Byron usually arrives around December 1, and the last of the season around March 17. Those are the middle dates across the winters of 1991–2020 at Geneseo, IL, 13.6 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 30 days after the last snow.
Planting calendar for 61275
| When | What to do |
|---|---|
| February 5 – February 19 | Start peppers and aubergines indoorsThey need eight to ten weeks under lights before they can go out. |
| February 19 – March 5 | Start tomatoes indoorsSix to eight weeks gives a transplant big enough to set fruit early. |
| March 19 – April 2 | Sow peas, spinach, lettuce, radish outdoorsThese tolerate light frost and prefer to germinate in cool soil. |
| April 16 onward | Transplant tomatoes, peppers, basil, squash, cucumbersThe average last freeze has passed — still watch the actual forecast. |
| by August 2 | Sow the autumn crop of carrots, beets and brassicasThey need about twelve weeks to size up before growth stops. |
| by October 11 | Harvest tender crops, or be ready to cover themA first freeze two weeks early is well within normal variation. |
| October 25 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 61275 is 5 miles from Le Claire L&D 14, IA, which stands at 577 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 4 other ZIP codes share the station; its figures are presented in full for 61244 (East Moline). The 2023 USDA Plant Hardiness Zone Map lists ZIP 61275 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.