When is the last frost in Denver, CO?

The average last spring frost (50% probability of 32°F) in Denver is around April 30, based on NOAA/NCEI 1991–2020 normals at the Denver Water Dept, CO station (1.6 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 Denver?

The average first fall frost in Denver, CO is around October 12, giving roughly a 165-day frost-free growing season.

What planting zone is Denver, CO?

Denver is in USDA plant hardiness zone 6a (average annual extreme minimum temperature -10 to -5°F), from the 2023 USDA Plant Hardiness Zone Map.

What is the weather like in Denver?

In Denver, CO the warmest month is July (avg high 91.4°F) and the coldest is December (avg low 20.6°F). It averages about 15.9″ of precipitation a year and 40.7″ of snow.

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Denver, CO Planting Calendar & Frost Dates

USDA hardiness zone 6a · ZIP 80202 · elevation 1594′ · NOAA & USDA data

Denver is in USDA hardiness zone 6a (winters can dip to -10 to -5°F), with a growing season of about 165 days between the average last spring frost (April 30) and first fall frost (October 12). The warmest month is July (avg high 91.4°F); the coldest is December (avg low 20.6°F). It averages 15.9″ of precipitation a year and 40.7″ 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 -10 to -5°F

Last spring frost

April 30

avg (50% prob, 32°F)

First fall frost

October 12

avg (50% prob, 32°F)

Growing season

165 days

frost-free window

Warmest month

July

avg high 91.4°F

Month-by-month typical weather in Denver

Average conditions from the NOAA/NCEI 1991–2020 U.S. Climate Normals at Denver Water Dept, CO (1.6 mi away). Temperatures °F, precipitation & snow in inches.

Month	Avg high	Avg low	Mean	Precip (in)	Snow (in)
January	48.5	21.3	34.9	0.4	5.5
February	49	21.7	35.4	0.6	8.4
March	57.9	29.6	43.7	1.1	9.2
April	64.1	36.2	50.1	2	5
May	73	45.9	59.4	2.7	0.9
June	85.3	55.8	70.6	1.7	0
July	91.4	61.8	76.6	1.9	0
August	89.6	60.1	74.8	1.8	0
September	81.6	50.7	66.2	1.2	0
October	67.6	37.7	52.6	1.2	2.5
November	55.9	27.6	41.7	0.8	4.4
December	47.3	20.6	34	0.5	4.8

What to plant when in Denver

Crop	Season	What to do & when
Tomatoes	warm	Start seeds indoors: March 19 · Transplant out: May 7
Peppers	warm	Start seeds indoors: March 5 · Transplant out: May 14
Cucumbers	warm	Direct sow: May 7
Zucchini / squash	warm	Direct sow: May 7
Bush beans	warm	Direct sow: May 7
Sweet corn	warm	Direct sow: May 7
Basil	warm	Transplant out: May 7
Peas	cool	Sow (spring): March 26 · Sow (fall): August 17
Spinach	cool	Sow (spring): March 19 · Sow (fall): August 17
Lettuce	cool	Sow (spring): April 2 · Sow (fall): August 17
Kale	cool	Transplant (spring): April 9 · Sow (fall): August 3
Broccoli	cool	Transplant (spring): April 16
Carrots	cool	Sow (spring): April 9 · Sow (fall): August 3
Onions	cool	Transplant (spring): April 2
Potatoes	cool	Plant seed potatoes: April 16
Radishes	cool	Sow (spring): April 2 · Sow (fall): August 31

Dates are computed from Denver'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 Colorado

Westminster, CO Arvada, CO Aurora, CO Littleton, CO Thornton, CO Broomfield, CO Commerce City, CO Parker, CO

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 — Denver Water Dept, CO, 1.6 mi (confidence: high). Monthly weather normals: Denver Water Dept, CO, 1.6 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.