When is the last frost in St. Charles, MO?

The average last spring frost (50% probability of 32°F) in St. Charles is around April 8, based on NOAA/NCEI 1991–2020 normals at the St Charles Elm Pt, MO station (4.1 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 St. Charles?

The average first fall frost in St. Charles, MO is around October 29, giving roughly a 203-day frost-free growing season.

What planting zone is St. Charles, MO?

St. Charles is in USDA plant hardiness zone 6b (average annual extreme minimum temperature -5 to 0°F), from the 2023 USDA Plant Hardiness Zone Map.

What is the weather like in St. Charles?

In St. Charles, MO the warmest month is July (avg high 88°F) and the coldest is January (avg low 21.9°F). It averages about 45.7″ of precipitation a year and 9″ of snow.

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St. Charles, MO Planting Calendar & Frost Dates

USDA hardiness zone 6b · ZIP 63301 · elevation 144′ · NOAA & USDA data

St. Charles is in USDA hardiness zone 6b (winters can dip to -5 to 0°F), with a growing season of about 203 days between the average last spring frost (April 8) and first fall frost (October 29). The warmest month is July (avg high 88°F); the coldest is January (avg low 21.9°F). It averages 45.7″ of precipitation a year and 9″ 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 -5 to 0°F

Last spring frost

April 8

avg (50% prob, 32°F)

First fall frost

October 29

avg (50% prob, 32°F)

Growing season

203 days

frost-free window

Warmest month

July

avg high 88°F

Month-by-month typical weather in St. Charles

Average conditions from the NOAA/NCEI 1991–2020 U.S. Climate Normals at St Charles Elm Pt, MO (4.1 mi away). Temperatures °F, precipitation & snow in inches.

Month	Avg high	Avg low	Mean	Precip (in)	Snow (in)
January	39.5	21.9	30.7	2.7	4.3
February	44.7	25.2	35	2.9	2.6
March	55.2	33.7	44.4	3.6	0.5
April	66.8	44	55.4	5.1	0
May	76	55.1	65.5	5.5	0
June	84.1	64.3	74.2	4.4	0
July	88	68.3	78.2	4.2	0
August	86.8	65.8	76.3	4.1	0
September	80.4	57.2	68.8	3.1	0
October	68.8	45.7	57.3	3.5	0
November	55.3	35.3	45.3	3.7	0.1
December	44.1	26.4	35.2	3	1.5

What to plant when in St. Charles

Crop	Season	What to do & when
Tomatoes	warm	Start seeds indoors: February 25 · Transplant out: April 15
Peppers	warm	Start seeds indoors: February 11 · Transplant out: April 22
Cucumbers	warm	Direct sow: April 15
Zucchini / squash	warm	Direct sow: April 15
Bush beans	warm	Direct sow: April 15
Sweet corn	warm	Direct sow: April 15
Basil	warm	Transplant out: April 15
Peas	cool	Sow (spring): March 4 · Sow (fall): September 3
Spinach	cool	Sow (spring): February 25 · Sow (fall): September 3
Lettuce	cool	Sow (spring): March 11 · Sow (fall): September 3
Kale	cool	Transplant (spring): March 18 · Sow (fall): August 20
Broccoli	cool	Transplant (spring): March 25
Carrots	cool	Sow (spring): March 18 · Sow (fall): August 20
Onions	cool	Transplant (spring): March 11
Potatoes	cool	Plant seed potatoes: March 25
Radishes	cool	Sow (spring): March 11 · Sow (fall): September 17

Dates are computed from St. Charles'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 Missouri

Florissant, MO St. Peters, MO Chesterfield, MO St. Louis, MO Jefferson City, MO Columbia, MO Cape Girardeau, MO Springfield, MO

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 — St Charles Elm Pt, MO, 4.1 mi (confidence: high). Monthly weather normals: St Charles Elm Pt, MO, 4.1 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.