When is the last frost in Crystal Lake, IL?

The average last spring frost (50% probability of 32°F) in Crystal Lake is around May 1, based on NOAA/NCEI 1991–2020 normals at the Mc Henry -Wg Stratton L&d, IL station (3.9 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 Crystal Lake?

The average first fall frost in Crystal Lake, IL is around October 11, giving roughly a 162-day frost-free growing season.

What planting zone is Crystal Lake, IL?

Crystal Lake 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 Crystal Lake?

In Crystal Lake, IL the warmest month is July (avg high 84.2°F) and the coldest is January (avg low 12.9°F). It averages about 37″ of precipitation a year and 34.5″ of snow.

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Crystal Lake, IL Planting Calendar & Frost Dates

USDA hardiness zone 5b · ZIP 60012 · elevation 224′ · NOAA & USDA data

Crystal Lake is in USDA hardiness zone 5b (winters can dip to -15 to -10°F), with a growing season of about 162 days between the average last spring frost (May 1) and first fall frost (October 11). The warmest month is July (avg high 84.2°F); the coldest is January (avg low 12.9°F). It averages 37″ of precipitation a year and 34.5″ 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

May 1

avg (50% prob, 32°F)

First fall frost

October 11

avg (50% prob, 32°F)

Growing season

162 days

frost-free window

Warmest month

July

avg high 84.2°F

Month-by-month typical weather in Crystal Lake

Average conditions from the NOAA/NCEI 1991–2020 U.S. Climate Normals at Mc Henry -Wg Stratton L&d, IL (3.9 mi away). Temperatures °F, precipitation & snow in inches.

Month	Avg high	Avg low	Mean	Precip (in)	Snow (in)
January	30.6	12.9	21.7	1.7	11
February	34.6	16.2	25.4	1.6	8.9
March	46	25.9	35.9	2.2	3.9
April	58.8	36.6	47.7	3.6	1
May	70.4	47.2	58.8	4.5	0
June	80.2	57	68.6	4.8	0
July	84.2	61.5	72.8	3.8	0
August	82.3	59.7	71	3.7	0
September	75.7	51.4	63.6	3.6	0
October	63	39.6	51.3	3.2	0.1
November	48.1	29.4	38.7	2.4	1.4
December	35.9	19.3	27.6	1.9	8.2

What to plant when in Crystal Lake

Crop	Season	What to do & when
Tomatoes	warm	Start seeds indoors: March 20 · Transplant out: May 8
Peppers	warm	Start seeds indoors: March 6 · Transplant out: May 15
Cucumbers	warm	Direct sow: May 8
Zucchini / squash	warm	Direct sow: May 8
Bush beans	warm	Direct sow: May 8
Sweet corn	warm	Direct sow: May 8
Basil	warm	Transplant out: May 8
Peas	cool	Sow (spring): March 27 · Sow (fall): August 16
Spinach	cool	Sow (spring): March 20 · Sow (fall): August 16
Lettuce	cool	Sow (spring): April 3 · Sow (fall): August 16
Kale	cool	Transplant (spring): April 10 · Sow (fall): August 2
Broccoli	cool	Transplant (spring): April 17
Carrots	cool	Sow (spring): April 10 · Sow (fall): August 2
Onions	cool	Transplant (spring): April 3
Potatoes	cool	Plant seed potatoes: April 17
Radishes	cool	Sow (spring): April 3 · Sow (fall): August 30

Dates are computed from Crystal Lake'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

Carpentersville, IL Hoffman Estates, IL Elgin, IL Palatine, IL Streamwood, IL Buffalo Grove, IL Schaumburg, IL Arlington Heights, 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 — Mc Henry -Wg Stratton L&d, IL, 3.9 mi (confidence: high). Monthly weather normals: Mc Henry -Wg Stratton L&d, IL, 3.9 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.