When is the last frost in Naperville, IL?

The average last spring frost (50% probability of 32°F) in Naperville is around April 28, based on NOAA/NCEI 1991–2020 normals at the Lisle-morton Arboretum, IL station (5 mi away). Half of years it falls outside that date, so wait 1–2 weeks past it before setting out frost-tender plants.

When is the first fall frost in Naperville?

The average first fall frost in Naperville, IL is around October 16, giving roughly a 169-day frost-free growing season.

What planting zone is Naperville, IL?

Naperville is in USDA plant hardiness zone 5b (average annual extreme minimum temperature -15 to -10°F), from the 2023 USDA Plant Hardiness Zone Map.

What is the weather like in Naperville?

In Naperville, IL the warmest month is July (avg high 85.5°F) and the coldest is January (avg low 16.8°F). It averages about 39.9″ of precipitation a year and 24.3″ of snow.

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Naperville, IL Planting Calendar & Frost Dates

USDA hardiness zone 5b · ZIP 60540 · elevation 207′ · NOAA & USDA data

Naperville is in USDA hardiness zone 5b (winters can dip to -15 to -10°F), with a growing season of about 169 days between the average last spring frost (April 28) and first fall frost (October 16). The warmest month is July (avg high 85.5°F); the coldest is January (avg low 16.8°F). It averages 39.9″ of precipitation a year and 24.3″ of snow, mostly mid-winter. Start cool-season crops several weeks before the last frost; wait until after it for tomatoes, peppers and other tender crops.

Hardiness zone

min temp -15 to -10°F

Last spring frost

April 28

avg (50% prob, 32°F)

First fall frost

October 16

avg (50% prob, 32°F)

Growing season

169 days

frost-free window

Warmest month

July

avg high 85.5°F

Month-by-month typical weather in Naperville

Average conditions from the NOAA/NCEI 1991–2020 U.S. Climate Normals at Wheaton 3 Se, IL (5 mi away). Temperatures °F, precipitation & snow in inches.

Month	Avg high	Avg low	Mean	Precip (in)	Snow (in)
January	32.8	16.8	24.8	2.1	9.3
February	37.5	19.8	28.6	2	5.1
March	49.5	28.5	39	2.5	4.5
April	62.5	38.3	50.4	4.1	0.3
May	73.6	48.7	61.1	4.5	0
June	82.9	58.5	70.7	4.7	0
July	85.5	63.1	74.3	3.9	0
August	83.7	62.1	72.9	4.4	0
September	78	53.8	65.9	3.3	0
October	65.2	42.9	54	3.6	0
November	50.1	31.8	41	2.8	0.9
December	37.7	22.6	30.2	2.2	4.2

What to plant when in Naperville

Crop	Season	What to do & when
Tomatoes	warm	Start seeds indoors: March 17 · Transplant out: May 5
Peppers	warm	Start seeds indoors: March 3 · Transplant out: May 12
Cucumbers	warm	Direct sow: May 5
Zucchini / squash	warm	Direct sow: May 5
Bush beans	warm	Direct sow: May 5
Sweet corn	warm	Direct sow: May 5
Basil	warm	Transplant out: May 5
Peas	cool	Sow (spring): March 24 · Sow (fall): August 21
Spinach	cool	Sow (spring): March 17 · Sow (fall): August 21
Lettuce	cool	Sow (spring): March 31 · Sow (fall): August 21
Kale	cool	Transplant (spring): April 7 · Sow (fall): August 7
Broccoli	cool	Transplant (spring): April 14
Carrots	cool	Sow (spring): April 7 · Sow (fall): August 7
Onions	cool	Transplant (spring): March 31
Potatoes	cool	Plant seed potatoes: April 14
Radishes	cool	Sow (spring): March 31 · Sow (fall): September 4

Dates are computed from Naperville's average frost dates using standard cool-/warm-season timing. They're a starting point — a cold spring, a warm microclimate, or a fast-maturing variety can shift them by a week or two.

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Gear that helps you plant on time

Some links below are Amazon affiliate links (tag theboringthin-20). If you buy through them we may earn a small commission at no extra cost to you — it keeps this almanac free. We only list generic, genuinely-useful categories.

Soil thermometer →Know when the ground is warm enough to sow — the honest signal, not the calendar.Seed-starting trays + dome →Start tomatoes & peppers indoors on the schedule below.Seedling heat mat →Warms the soil for faster, more even germination indoors.Floating row cover / frost cloth →Buys you 4–8°F to beat an early or late frost.Raised garden bed kit →Warms and drains faster in spring than in-ground soil.Garden gloves →Basic kit for transplant day.

Nearby cities in Illinois

Aurora, IL Bolingbrook, IL Downers Grove, IL Wheaton, IL Romeoville, IL Lombard, IL Carol Stream, IL Plainfield, IL

Sources & method. Hardiness zone: 2023 USDA Plant Hardiness Zone Map (PRISM Climate Group, Oregon State University). Frost dates & growing season: NOAA/NCEI 1991–2020 U.S. Climate Normals, nearest station with published freeze normals — Lisle-morton Arboretum, IL, 5 mi (confidence: high). Monthly weather normals: Wheaton 3 Se, IL, 5 mi (confidence: high). ZIP centroid from U.S. Census 2023 ZCTA data. Frost dates are the 50%-probability date — half of years frost occurs outside the stated date. Nothing here is invented; where the nearest station is far, we say so. Last updated 2026-07-22.