Frost dates for Aurora, Illinois
In Aurora, half of springs have had their last frost by April 28 (and 1 spring in 10 still has one after May 11), and half of falls have had their first frost by October 13, leaving about 166 frost-free days in a typical year. Here is how sure those dates are, what they mean for planting, and where they come from.
Frost dates for
Aurora, Illinois
Last spring frost
April 28
Half of springs have their last frost by this date. For a safer bet, wait until May 11: only 1 spring in 10 has a frost after that.
First fall frost
October 13
Half of falls have their first frost by this date. In 1 fall in 10 it comes by September 27.
Growing season
166 days
Frost-free days in a typical year. 9 years in 10 get at least 145.
Hardiness zone
5b
2023 USDA map: the coldest night of winter averages −15°F to −10°F. It was 5b on the 2012 map too. All 11 ZIP codes within about 6 miles of the city's center are in zone 5b.
Print a year planner for Aurora
Frost risk through the year
How sure are these dates?
A frost date is a probability, not a promise. NOAA worked out, from 30 years of nightly lows, how often the last spring frost and the first fall frost fall on each date. The middle column is the typical year. The outer columns are the early and late years that come about once a decade.
| Early year 1 in 10 | Typical year 1 in 2 | Late year 1 in 10 | |
|---|---|---|---|
| Last frost in spring | April 14 | April 28 | May 11 |
| First frost in fall | September 27 | October 13 | October 24 |
The frost-free season between them runs 166 days in a typical year. In 1 year in 10 it is 185 days or longer, and in 1 year in 10 it is 145 days or shorter.
- Hard freeze (28°F): typically last on April 18 and first on October 23. It is a harder freeze than the 32°F frost line, cold enough to damage many garden plants; how hardy a crop is decides whether it comes through. (The National Weather Service's own hard-freeze threshold varies from office to office.)
- Frost possible (36°F at the station): typically last on May 6 and first on October 2. On clear, still nights the ground can be several degrees colder than the thermometer, so frost can form on plants when the official reading is in the mid-30s.
In 8 springs out of 10, the last frost in Aurora comes between April 14 and May 11, a window of 27 days. That is narrower than at most NOAA stations (the typical window is 31 days), so the typical date is a steadier guide here than in most places.
Among Illinois's 170 NOAA stations with a frost every year, 5 percent have their typical last frost later than Aurora does.
Planting calendar for Aurora
These dates count from the typical last and first frosts, using the planting rules published by Colorado State University Extension (spring), Virginia Cooperative Extension (fall crops) and University of Minnesota Extension (garlic, where winters are hard). Weather in any one year can run early or late, so check the forecast before you plant tender crops.
Your season is too short for a separate fall planting of cabbage: sown late enough to be a fall crop, it wouldn't be ready before the typical first frost. Your spring planting is your harvest.
| When | What to do | Why then |
|---|---|---|
| February | ||
| February 10 to March 10 | Broccoli and cabbage Start seeds indoors | 5 to 7 weeks before planting them out |
| February 24 to March 24 | Cauliflower Start seeds indoors | 5 to 7 weeks before planting out |
| March | ||
| March 10 to 31 | Eggplant Start seeds indoors | 6 to 9 weeks before planting out |
| March 17 to 31 | Peppers Start seeds indoors | 6 to 8 weeks before planting out |
| March 24 to April 7 | Tomatoes Start seeds indoors | 5 to 7 weeks before planting out |
| March 31 to April 14 | Peas, spinach, lettuce, radishes, onion sets, turnips Sow outdoors, as early as | hardy crops: 2 to 4 weeks before the typical last frost |
| March 31 to April 14 | Broccoli and cabbage Plant out, as early as | hardy crops: 2 to 4 weeks before the typical last frost |
| April | ||
| April 14 to 28 | Beets, carrots, potatoes, Swiss chard Plant outdoors, as early as | semi-hardy crops: up to 2 weeks before the typical last frost |
| April 14 to 28 | Cauliflower Plant out, as early as | semi-hardy: up to 2 weeks before the typical last frost |
| April 28 | Snap beans, sweet corn, cucumbers, summer squash Sow outdoors around | tender crops: around the typical last frost date |
| May | ||
| May 12 | Tomatoes, peppers, eggplant Plant out from | very tender: 2 weeks or more after the typical last frost |
| May 12 | Melons, winter squash, pumpkins, lima beans Sow outdoors from | very tender: 2 weeks or more after the typical last frost |
| June | ||
| June 7 to 21 | Broccoli for fall Start seeds | set the plants out by July 26 |
| July | ||
| July 17 | Snap beans for fall Last date to sow | 60 days to harvest, plus 2 weeks for slower fall growth, plus 2 weeks because frost kills it |
| July 21 | Carrots for fall Last date to sow | 70 days to harvest, plus 2 weeks for slower fall growth |
| July 22 | Cucumbers for fall Last date to sow | 55 days to harvest, plus 2 weeks for slower fall growth, plus 2 weeks because frost kills it |
| July 26 | Peas for fall Last date to sow | 65 days to harvest, plus 2 weeks for slower fall growth |
| July 27 | Summer squash for fall Last date to sow | 50 days to harvest, plus 2 weeks for slower fall growth, plus 2 weeks because frost kills it |
| July 31 | Leaf lettuce and beets for fall Last date to sow | 60 days to harvest, plus 2 weeks for slower fall growth |
| August | ||
| August 10 | Turnips and kohlrabi for fall Last date to sow | 50 days to harvest, plus 2 weeks for slower fall growth |
| August 20 | Spinach for fall Last date to sow | 40 days to harvest, plus 2 weeks for slower fall growth |
| August 30 | Radishes for fall Last date to sow | 30 days to harvest, plus 2 weeks for slower fall growth |
| September | ||
| September 27 | Tomatoes, peppers, squash, melons, cucumbers Watch the forecast from | in 1 fall in 10 the first frost comes by this date; pick tender crops before a frost |
| October | ||
| October 30 to November 6 | Garlic Plant cloves | one or two weeks after the typical first hard freeze (28°F), our reading of the first killing frost |
Want more insurance? Shift every spring date 13 days later. That plans around May 11, the date after which only 1 spring in 10 has a frost.
For spring bulbs such as tulips and daffodils, plant once the soil has cooled to about 50 to 55°F and keep going until a couple of weeks before the ground freezes. Our guide to fall planting explains how to tell.
Where these numbers come from
These dates come from NOAA's weather station Chicago Aurora Municipal Airport (station USW00004808), 10 miles from the center of Aurora. It sits at about the same elevation, 710 feet above sea level. NOAA rates this station's record as representative: at least 10 of the 30 years, with the gaps filled from nearby stations.
The same station also gives the frost dates for Plainfield, Oswego, Yorkville, Montgomery, North Aurora and Plano.
Our ZIP code lookup matches these 11 ZIP codes to the same station, so they get the same dates: 60119, 60144, 60511, 60512, 60520, 60536, 60545, 60548, 60552, 60554, 60560. Hardiness zones are worked out separately for each ZIP code.
Nearby places
- Naperville, Illinois: last frost around April 25, first frost around October 19 (7 miles away)
- Joliet, Illinois: last frost around April 19, first frost around October 25 (20 miles away)
- Chicago, Illinois: last frost around April 11, first frost around October 31 (30 miles away)
See frost dates across Illinois, or look up your own ZIP code for the station nearest you. Want the background? Read what a last frost date really means.