Thompson, Manitoba Garden Guide: Planting Dates, Frost Dates & Growing Season

Growing Season Snapshot

Typical last spring frost June 14

Typical first fall frost August 28

Typical frost-free days 75

GDD left on May 15 (base 50) 795

These season boundaries are climate normals, not a forecast. A 50% frost date means a 32°F frost arrives by that date in about half of years — and later in about half. Treat these dates as planning anchors, not guarantees.

Thompson Planting Calendar

A practical guide to when planting usually works in Thompson. These windows are based on climate normals (not a forecast) and line up with the 50% last spring frost and typical early-season heat.

Crop	Planting Window	Method	Best Variety	Local Fit
Cool-season / early window Cold-tolerant crops that usually handle cooler spring conditions better.
Peas	May 17 – May 31	direct sow	Little Marvel	Excellent fit
Spinach	May 17 – May 31	direct sow	Space	Excellent fit
Kale	May 21 – June 10	direct sow / transplant	Winterbor	Strong fit
Lettuce	May 24 – June 7	direct sow / transplant	Buttercrunch	Excellent fit
Strawberries	May 24 – June 7	plant crowns / transplants	Seascape	Excellent fit
Beets	May 24 – June 7	direct sow	Detroit Dark Red	Strong fit
Carrots	May 24 – June 7	direct sow	Bolero	Strong fit
Onions	May 24 – June 7	sets / transplants	Walla Walla	Borderline
Swiss Chard	May 25 – June 14	direct sow / transplant	Bright Lights	Strong fit
Broccoli	May 31 – June 14	transplant	Packman	Strong fit
Cabbage	May 31 – June 14	transplant	Stonehead	Strong fit
Cauliflower	May 31 – June 14	transplant	Snow Crown	Strong fit
Potatoes	May 31 – June 14	plant seed potatoes	Dark Red Norland	Good fit
Main warm-season window Crops that usually do best once frost risk fades and the season starts opening up more fully.
Beans	June 14 – June 28	direct sow	Provider	Risky fit
Sweet Corn	June 19 – June 29	direct sow	Yukon Chief	Risky fit
Basil	June 23 – July 3	direct sow / transplant	Prospera	Borderline
Cucumbers	June 23 – July 3	direct sow / transplant	Cool Breeze	Borderline
Zucchini	June 23 – July 3	direct sow / transplant	Dunja	Borderline
Melons	June 23 – July 3	direct sow / transplant	Minnesota Midget	Risky fit
Pumpkin	June 23 – July 3	direct sow / transplant	Small Sugar	Risky fit
Tomatoes	June 23 – July 3	transplant	Stupice	Risky fit
Watermelons	June 23 – July 3	direct sow / transplant	Sugar Baby	Risky fit
Winter Squash	June 23 – July 3	direct sow / transplant	Delicata	Risky fit
Peppers	June 30 – July 10	transplant	King of the North	Risky fit

How to use this: aim for the earlier part of each window for the most reliable results. Later planting can still work, but it usually depends more on variety maturity, warmer microclimates, and simple protection like row cover or low tunnels.

Common Timing Mistakes

These patterns show up again and again in Thompson — especially in typical years.

Starting warm-season crops too late — even small delays can mean they never finish.
Choosing long-season varieties that need more heat than a typical year provides.
Expecting late plantings to finish — cooling nights often slow crops earlier than expected.
Relying on calendar dates instead of crop maturity and typical frost timing.

Missed Your Planting Window? What Can You Still Grow?

This table shows what can still mature from several later-season planting dates in Thompson. It compares the growing degree days still typically available after each checkpoint with the heat each crop usually needs to finish, then applies a 15% safety margin to separate crops that usually still fit from ones that are more borderline.

Usually fits Borderline Too tight

Crop	Heat Units	May 15	Jun 1	Jul 1	Aug 1
Spinach	450 (base 40)	✅	✅	✅	✅
Lettuce	500 (base 40)	✅	✅	✅	✅
Strawberry	600 (base 40)	✅	✅	✅	✅
Pea	600 (base 40)	✅	✅	✅	✅
Beet	650 (base 40)	✅	✅	✅	✅
Basil	700 (base 50)	⚠️	⚠️	❌	❌
Kale	700 (base 40)	✅	✅	✅	✅
Zucchini	750 (base 50)	⚠️	⚠️	❌	❌
Carrot	750 (base 40)	✅	✅	✅	⚠️
Swiss chard	750 (base 40)	✅	✅	✅	⚠️
Cucumber	800 (base 50)	❌	❌	❌	❌
Broccoli	900 (base 40)	✅	✅	✅	❌
Bean	900 (base 50)	❌	❌	❌	❌
Cabbage	1000 (base 40)	✅	✅	✅	❌
Cauliflower	1000 (base 40)	✅	✅	✅	❌
Sweet corn	1100 (base 50)	❌	❌	❌	❌
Potato	1100 (base 45)	✅	✅	❌	❌
Melon	1200 (base 50)	❌	❌	❌	❌
Tomato	1200 (base 50)	❌	❌	❌	❌
Pepper	1300 (base 50)	❌	❌	❌	❌
Onion	1300 (base 45)	⚠️	⚠️	❌	❌
Winter squash	1300 (base 50)	❌	❌	❌	❌
Pumpkin	1300 (base 50)	❌	❌	❌	❌
Watermelon	1350 (base 50)	❌	❌	❌	❌

Climate normals GDD planning

Compare your season’s typical heat accumulation against crop requirements before first fall frost.

Heat matters more than calendar days Use this when crop maturity depends on warmth, not just frost-free days. Especially useful for warm-season crops and short-season locations.

Best for borderline crops Especially useful for warm-season crops and short-season locations.

Check Crop Maturity and Timing in Thompson

Enter a ZIP / Postal Code in Thompson and your planting date to see whether different crops can typically mature before first fall frost.

ZIP / Postal

Crops

Select one or more crops.

Select Outdoor sow / Transplant date

How the Growing Season Works in Thompson

Thompson is a short-season growing environment. The season closes quickly enough that variety maturity, planting timing, and early establishment usually matter more than small differences in calendar timing.

Warm-season crops: usually perform best when they are established promptly after the last spring frost.
Variety maturity matters: shorter-season cultivars are often the safer choice than longer-season bets.
Protection can help: row cover, transplants, and sheltered spots often improve consistency in a short season.

Late-summer note: by early August, the remaining heat often tightens quickly. Late plantings tend to work best when they are fast, cold-tolerant, or protected.

Remaining Season Heat in Thompson (Base 50 GDD)

Growing Degree Days (Base 50°F) measure heat accumulation. “Remaining GDD” shows how much usable heat is typically still available from a given date onward in a normal season.

Planting date	Base	Typical GDD still available
May 15	50	795
June 1	50	791
July 1	50	622
August 1	50	266

Use these values to judge whether a crop or variety still has enough heat left after planting. This is especially helpful for later sowings, shorter-maturity choices, and deciding whether a second round is realistic.

How Gardeners Adapt

Experienced gardeners in Thompson usually adjust their timing and crop choices to match how the season actually behaves, not just the calendar.

Starting warm-season crops indoors to gain extra time early in the season.
Choosing short-season or faster-maturing varieties whenever possible.
Using row cover or low tunnels to smooth out temperature swings early and late in the season.
Succession planting fast crops to keep beds productive through summer.
Shifting late plantings toward greens, roots, and other reliable short-season crops.
Watching local conditions closely and adjusting timing year by year.

Thompson Garden Planning Chart

A practical “typical year” for planning. Use it as a baseline, then adjust for microclimates and variety maturity.

Stage	What it usually means
Early season	Start cold-tolerant crops, prep beds, and pay more attention to soil warmth and night temperatures than to the calendar alone.
Main planting	Around June 14, the main planting push usually begins as frost risk fades. Warm-season crops generally perform best when they get established promptly.
Peak growth	This is when water, fertility, spacing, and pest pressure have the biggest effect on final yield.
Late-summer decisions	Late plantings are usually tight, so fast crops and protected spots become much more important.
Finish window	Plan to have frost-sensitive crops mostly wrapped up by August 28. Cooling nights often slow crops before the first real frost arrives.

Typical season length: 75 frost-free days between the median spring and fall frost dates.

Crop Guides for Thompson

Published crop-specific planting guides for Thompson, ordered from best fit to highest risk.

Excellent fit

Lettuce

Lettuce is usually one of the easier crops to grow here.

When to Plant Lettuce in Thompson

Peas

Thompson usually gives peas enough season that maturity is rarely the hard part.

When to Plant Peas in Thompson

Spinach

Spinach performs easily here in a typical year.

When to Plant Spinach in Thompson

Strawberries

This crop usually has enough season here that maturity is rarely the hard part.

When to Plant Strawberries in Thompson

Strong fit

Beets

Beets are usually a dependable crop choice here.

When to Plant Beets in Thompson

Broccoli

Thompson usually gives broccoli enough season for reliable maturity.

When to Plant Broccoli in Thompson

Cabbage

Cabbage performs well here when planted on time.

When to Plant Cabbage in Thompson

Carrots

This crop usually gives gardeners some real room to work with.

When to Plant Carrots in Thompson

Cauliflower

Early and mid-season varieties usually fit well here.

When to Plant Cauliflower in Thompson

Kale

Kale is usually a dependable crop choice here.

When to Plant Kale in Thompson

Swiss Chard

Thompson usually gives swiss chard enough season for reliable maturity.

When to Plant Swiss Chard in Thompson

Good fit

Potatoes

Potatoes are usually a practical crop here with good timing.

When to Plant Potatoes in Thompson

Borderline

Basil

Basil can work here, but timing and variety choice matter a lot.

When to Plant Basil in Thompson

Cucumbers

Thompson can support cucumbers, though the margin is not generous.

When to Plant Cucumbers in Thompson

Onions

This crop stays closer to the edge of the season than easier choices do.

When to Plant Onions in Thompson

Zucchini

Earlier varieties and warmer spots usually improve the odds here.

When to Plant Zucchini in Thompson

Risky fit

Beans

Beans are harder to finish well here and usually needs the fastest approach.

When to Plant Beans in Thompson

Melons

Thompson usually gives melons a narrow margin for maturity.

When to Plant Melons in Thompson

Peppers

This is a higher-risk crop here unless the site and timing are especially favorable.

When to Plant Peppers in Thompson

Pumpkin

Growers usually do best with quick varieties and the warmest spots they have.

When to Plant Pumpkin in Thompson

Sweet Corn

Very early varieties usually have the best chance here.

When to Plant Sweet Corn in Thompson

Tomatoes

Tomatoes are harder to finish well here and usually needs the fastest approach.

When to Plant Tomatoes in Thompson

Watermelons

Thompson usually gives watermelons a narrow margin for maturity.

When to Plant Watermelons in Thompson

Winter Squash