Seasonal guide · Thunder Bay, ON
Thunder Bay Lawn Care Calendar: How to Use a Short Season Well
In Thunder Bay, the lawn season runs from about late April to early November. Clean up once the snow is gone and the ground is dry. Start mowing in May when the grass grows. Cut taller in summer, then lower the mower in mid to late September. Clear leaves for the City's fall pickups, set for October 6 to 16 and November 3 to 13 in 2026. Make the last cut once October highs drop below 10°C.
Why is the lawn season so short in Thunder Bay?
Thunder Bay is cold for a long part of the year. Environment Canada's newer 1981 to 2010 climate normals skip the city, so we use its 1971 to 2000 set for the airport. Here is what those numbers say about the growing months:
| Month | Normal daily high | Nights at or below 0°C |
|---|---|---|
| April | 9.0°C | about 23 |
| May | 16.4°C | about 10 |
| June | 20.6°C | about 1 every 2 years |
| July | 24.2°C | none |
| August | 23.1°C | almost none |
| September | 17.1°C | about 5 |
| October | 10.4°C | about 18 |
| November | 1.7°C | most nights |
That leaves about six months of real lawn work. Frost can even show up in summer. The airport hit -2.8°C on June 7, 1949, and -1.1°C on August 29, 1976. So every job needs to happen on time. A missed month in a short season shows.
The good news is the rain. June through September each bring about 86 to 89 mm. That keeps grass growing steadily all summer, so the mowing never really takes a break.
What should you do in April?
April is cleanup month. The normals show snow on the ground at the end of March, about 13 cm, and none by the end of April. Wait for the snow to go and the lawn to firm up before you start.
Don't rush onto soggy grass. UConn Extension says walking or working on wet soil packs it down. That compaction can hurt the lawn all season. Give it a few dry days first.
Once it's dry, here's the spring list:
- Pick up sticks, branches and anything the snow hid.
- Rake out old leaves. UConn says leftover leaves slow spring green-up.
- Bag leaves and twigs in kraft paper bags for the City's spring pickup.
- Get the mower blade sharpened before the first cut.
- Trim evergreen hedges. Iowa State Extension says April is a good time to start.
The City runs two leaf and yard waste pickup days each spring. Look for the leaf symbol on your waste collection calendar to find yours. A spring cleanup from your crew can be timed for those days.
When should you start mowing in Thunder Bay?
Start when the grass starts growing, not on a set date. The Guelph Turfgrass Institute says cool-season grass starts to grow when the soil warms to 4.5 to 7°C (40 to 45°F). In Thunder Bay, that usually means late April or May. The normal May high is 16.4°C.
May still brings about 10 frosty nights in an average year. That's fine for grass. Just don't mow while the lawn is white with frost. Wait until it thaws.
For the first few cuts, Iowa State says to mow at 6.5 to 7.5 cm (2.5 to 3 inches) in spring. Never take off more than one third of the blade in one cut. If the grass got long, cut it down over two mows, a few days apart.
How should you mow from June to August?
Raise the mower for summer. Iowa State says 7.5 to 9 cm (3 to 3.5 inches) is right for summer months. The taller blades shade and cool the base of the plant. That helps on the hottest days in July, when the normal high is 24.2°C.
With steady summer rain, most lawns need a cut every week. Here's how to keep up:
- Mow on a fixed day each week so the grass never gets ahead of you.
- Keep to the one-third rule, even after a wet week.
- Leave the clippings on the lawn. The City calls this grasscycling.
- Trim along fences, walks and beds every time you mow.
Leaving clippings matters here for another reason. Thunder Bay does not take grass clippings in its leaf and yard waste program. So bagging them gives you a problem with nowhere easy to go.
Edges grow fast in summer too. See what trimming and edging covers if the strip along your fence keeps getting away from you.
What about hedges in summer?
Iowa State says most hedges need 2 to 4 trims a season. Light pruning in mid-summer is fine. Before you trim, look for nests. Environment and Climate Change Canada says bird nesting can run from mid-March to late August. Take care not to harm nests or eggs. Your crew can handle hedge and shrub trimming on the same visits.
What changes in September?
September still has a normal high of 17.1°C, so the grass keeps growing. But about 5 nights dip to freezing. It's time to start winding down.
Iowa State says to lower the mower in mid to late September. Go from 7.5 to 9 cm (3 to 3.5 inches) down to 6.5 to 7.5 cm (2.5 to 3 inches). Drop it one notch at a time over a few cuts. That way no single cut takes off more than a third.
The first leaves start to fall now too. Mow over a thin layer or rake it up. Don't let it build. Iowa State says leaf debris blocks light the grass needs before winter.
When is fall leaf pickup in Thunder Bay?
The City has two fall leaf and yard waste pickups in 2026. Both happen on your regular recycling day:
| Pickup | 2026 dates |
|---|---|
| First fall collection | October 6 to 16 |
| Second fall collection | November 3 to 13 |
Put your bags out before 7 am. Follow these City rules so they get taken:
- Use kraft paper bags only. There is no limit on how many.
- Keep each bag under 18 kg (40 lb).
- Tie branches with twine. Keep bundles under 1 m (39 inches) long and 61 cm (24 inches) around.
- No grass clippings.
- Don't rake or blow leaves into the street or near storm drains.
- Keep leaves off wooden fences.
Missed both days? You can take leaves, shrubs and branches to the compost area at the landfill, 5405 Mapleward Road. It's open 8 am to 6:30 pm on weekdays and 8 am to 4:30 pm on Saturdays. It's closed Sundays and stat holidays.
When is the last mow in Thunder Bay?
Iowa State says grass stops growing once daytime highs stay below 10°C (50°F). Thunder Bay's normal October high is 10.4°C, right on that line. November drops to 1.7°C. So growth winds down through October and is done by November.
Keep cutting while it still grows. Make your last cut at the low end of the fall range, about 6.5 cm (2.5 inches). Then clear the leaves one more time. The University of Saskatchewan says long, matted grass and leaf litter left over winter can lead to snow mould. Thunder Bay gets about 188 cm of snow in a normal year, so this is worth the effort.
Hold off on cutting back cedars and other evergreens now. Iowa State says evergreens pruned in fall are more likely to get winter injury. We go into more detail in when to stop mowing in Sudbury, which has a similar fall.
Does the long grass by-law apply all season?
Yes. Thunder Bay's Clean and Clear Yards By-law, BL 93/2022, says grass on private land can't grow past 20 cm (about 8 inches). The City also says boulevard grass should not grow over 20 cm. If you don't have a boulevard garden, you keep that strip cut too.
A missed week in June can push a lawn a long way. That's when people get caught. Weekly cuts keep you well clear of the limit. Weeds bothering you? Our partner crews don't spray, and we don't give advice on weed killers or other chemicals.
Can someone else follow this calendar for you?
Yes. Golden Oak Lawn Care matches you with a vetted, insured local crew in Thunder Bay. They do the work. We stand behind it with the Golden Oak Guarantee. Your crew can do the spring cleanup, weekly lawn mowing all summer, and the fall leaf work timed to the City's pickups.
We price every lawn by its size from satellite images. You get your price by text in 60 minutes. You keep the same crew every visit, and they text you a photo after every cut. Book the season through the Worry-Free Lawn Season and your first cut is free. Learn more on our Thunder Bay lawn care page.
Want it handled? Get your price in 60 minutes, or call 1-866-904-LAWN.
Thunder Bay Lawn Calendar Questions
When does lawn season start in Thunder Bay?
Cleanup can start once the snow is gone and the ground is dry, which is often late April. Mowing starts when the grass grows, usually in May. Grass wakes up when the soil reaches about 4.5 to 7°C.
Does Thunder Bay pick up grass clippings?
No. Grass clippings are not accepted in the City's leaf and yard waste program. The City says to leave them on the lawn instead. They break down and feed the grass.
What if I miss the fall leaf pickup days?
You can take leaves, shrubs and branches to the compost area at the landfill on Mapleward Road. It's open weekdays and Saturdays. You can also hold bags for the next pickup if one is still coming.
How tall should I cut my grass in summer?
About 7.5 to 9 cm (3 to 3.5 inches). Drop to 6.5 to 7.5 cm in spring and fall. Never cut more than one third of the blade at once.
Rules change, so check with the City before you plan. Sources: Leaf and Yard, fall 2026 collection dates, Landfill, City by-laws, Boulevard By-law, Thunder Bay climate normals, Guelph Turfgrass Institute, UConn soil compaction, UConn leaves, Iowa State mowing height, Iowa State fall lawn care, Iowa State: when to stop mowing, Iowa State hedges, Iowa State pruning times, ECCC nesting periods, USask snow mould.
