USDA Hardiness Zone 5b
Frost Dates for 60504 — Aurora, Illinois
NOAA 1991–2020 normals from Aurora, IL (660 ft), 3 miles northwest.
Updated
In Aurora, the last spring frost (32°F) is around April 19 in half of years and has passed by May 4 in nine years out of ten. The first fall frost comes around October 23, as early as October 9 one year in ten, leaving a typical freeze-free season of 185 days (NOAA, Aurora, IL).
- Last spring frost
- April 19
- First fall frost
- October 23
- Growing season
- 185 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 2
- Last snow
- March 18
- Winters with snow
- 100%
- Snow per year
- 27.9"
median, 1991–2020
median, 1991–2020
30 of 30 observed
NOAA normal
Frost risk by date in Aurora
Half of springs at Aurora, IL see their last 32°F night by April 19; only one in ten is past it by April 5, and one in ten still has one after May 4. Planting tender crops after April 25 leaves a 30% risk of a frost on them, after April 29 20%, and after May 4 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 23 in half of years, as early as October 9 one year in ten, and holds off past November 3 one year in ten. A hard freeze of 28°F follows 10 days later, around November 2; in spring the one-in-ten date for 28°F is April 23, 11 days before the 32°F one. The freeze-free season lasts 185 days in a typical year, longer than at 50% of the 158 Illinois stations; it reaches 205 days one year in ten and falls short of 164 one year in ten. On average 134 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 12 days longer, to about May 1, and return around October 13. Severe cold of 16°F or below comes every winter, usually between November 30 and March 7.
| Low | 90% | 80% | 70% | 60% | 50% | 40% | 30% | 20% | 10% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Apr 17 | Apr 21 | Apr 25 | Apr 29 | May 1 | May 4 | May 7 | May 12 | May 19 |
| 32°F | Apr 5 | Apr 10 | Apr 13 | Apr 16 | Apr 19 | Apr 22 | Apr 25 | Apr 29 | May 4 |
| 28°F | Mar 25 | Mar 31 | Apr 3 | Apr 5 | Apr 8 | Apr 12 | Apr 15 | Apr 18 | Apr 23 |
| 24°F | Mar 11 | Mar 17 | Mar 22 | Mar 26 | Mar 30 | Apr 1 | Apr 3 | Apr 7 | Apr 13 |
| 20°F | Mar 1 | Mar 7 | Mar 10 | Mar 13 | Mar 17 | Mar 20 | Mar 24 | Mar 29 | Apr 1 |
| 16°F | Feb 20 | Feb 27 | Mar 2 | Mar 5 | Mar 7 | Mar 10 | Mar 14 | Mar 19 | Mar 24 |
| Low | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Sep 29 | Oct 4 | Oct 8 | Oct 10 | Oct 13 | Oct 15 | Oct 18 | Oct 21 | Oct 25 |
| 32°F | Oct 9 | Oct 15 | Oct 18 | Oct 21 | Oct 23 | Oct 25 | Oct 28 | Oct 30 | Nov 3 |
| 28°F | Oct 21 | Oct 25 | Oct 29 | Oct 31 | Nov 2 | Nov 5 | Nov 8 | Nov 11 | Nov 16 |
| 24°F | Nov 1 | Nov 3 | Nov 7 | Nov 10 | Nov 12 | Nov 14 | Nov 17 | Nov 21 | Nov 26 |
| 20°F | Nov 8 | Nov 12 | Nov 15 | Nov 18 | Nov 21 | Nov 24 | Nov 27 | Dec 1 | Dec 6 |
| 16°F | Nov 15 | Nov 20 | Nov 24 | Nov 27 | Nov 30 | Dec 2 | Dec 6 | Dec 11 | Dec 18 |
Freeze probabilities 1991–2020 at Aurora, 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 60504 →Compare Aurora with another place →
Weather by month in Aurora
July is the warmest month at Aurora, IL, averaging 84°F by day and 65°F at night; January is the coldest at 31°F and 16°F. A freezing night is all but certain in every month from November 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 15% of years.
Warmth for growing adds up to 3,204 growing degree days a year (base 50°F), fewer than at 72% of the 158 Illinois stations. 34% of them (1,085) have built up by the end of June, and July adds the most, 756. Precipitation totals 39.7 inches a year, most in May (4.9") 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 | 31 | 16 | 1.9 | 100% | 29 | 0 |
| Feb | 35 | 20 | 1.8 | 100% | 26 | 2 |
| Mar | 47 | 29 | 2.4 | 100% | 22 | 27 |
| Apr | 60 | 39 | 4.1 | 97% | 7 | 108 |
| May | 71 | 50 | 4.9 | 15% | 1 | 340 |
| Jun | 81 | 60 | 4.5 | 0% | 0 | 609 |
| Jul | 84 | 65 | 4.2 | 0% | 0 | 756 |
| Aug | 82 | 63 | 3.9 | 0% | 0 | 701 |
| Sep | 76 | 55 | 3.4 | 2% | <1 | 469 |
| Oct | 63 | 43 | 3.7 | 82% | 5 | 166 |
| Nov | 48 | 32 | 2.7 | 100% | 17 | 24 |
| Dec | 36 | 22 | 2.2 | 100% | 27 | 2 |
Monthly normals 1991–2020 at Aurora, IL (660 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, Lisle-Morton Arboretum, IL, 10 miles east of Aurora, has a last frost 9 days later (April 28), a first frost 7 days earlier (October 16), a season 16 days shorter.
When it snows in Aurora, Illinois
The first measurable snow (0.1 inch or more) in Aurora usually arrives around December 2, and the last of the season around March 18. Those are the middle dates across the winters of 1991–2020 at Aurora, IL, 3.3 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 32 days after the last snow.
Planting calendar for 60504
| When | What to do |
|---|---|
| February 8 – February 22 | Start peppers and aubergines indoorsThey need eight to ten weeks under lights before they can go out. |
| February 22 – March 8 | Start tomatoes indoorsSix to eight weeks gives a transplant big enough to set fruit early. |
| March 22 – April 5 | Sow peas, spinach, lettuce, radish outdoorsThese tolerate light frost and prefer to germinate in cool soil. |
| April 19 onward | Transplant tomatoes, peppers, basil, squash, cucumbersThe average last freeze has passed — still watch the actual forecast. |
| by July 31 | Sow the autumn crop of carrots, beets and brassicasThey need about twelve weeks to size up before growth stops. |
| by October 9 | Harvest tender crops, or be ready to cover themA first freeze two weeks early is well within normal variation. |
| October 23 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 60504 is 3 miles from Aurora, IL, which stands at 660 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 9 other ZIP codes share the station; its figures are presented in full for 60505 (Aurora). The 2023 USDA Plant Hardiness Zone Map lists ZIP 60504 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.