When to Open Your Pool in Missoula, MT: Best Dates & Checklist

Missoula opening dates at a glance

Missoula banks only about 57 days of 80°F-plus afternoons — early opening weeks are the cheapest season extension available.

The same model in water terms: Missoula's estimated pool temperature runs about 44°F in mid-April, 59°F in mid-June, 69°F in mid-August, and 48°F in mid-October, peaking near 70°F. Those four checkpoints — not any calendar holiday — are what the windows above are protecting.

The 12-step Missoula opening checklist

Sequenced for a May 31–June 21 window: the first five steps are one honest afternoon, the middle is a 24-hour pump run, and the rest is testing patience. Chemical steps always defer to the product label; the un-dated generic version of this sequence lives in the how-to guide.

1. Pump off and clear the winter cover

   Use a cover pump on the standing water first, then sweep and pull the cover without spilling winter debris into the pool. To hit Missoula's June 7 target, this is the weekend-one job.

2. Top up the water level

   Set the garden hose in and bring the level to the skimmer's midpoint. That height is what lets the skimmer pull a proper surface current once the pump starts.

3. Remove winter plugs and reinstall fittings

   Pull expansion plugs and the skimmer guard, then refit return eyeballs, baskets, and ladders. Check each gasket as you go; a cracked one now is a mystery air leak later.

4. Reassemble the equipment pad

   Reinstall drain plugs on the pump, filter, and heater; lube o-rings with the manufacturer-recommended lubricant; reconnect unions hand-tight plus a quarter turn.

5. Prime the pump and run for 24 hours

   Water in the strainer pot, air relief open, power on — then leave it alone for a full day. Continuous turnover does the first and biggest share of the clearing work before chemistry even enters the picture.

6. Service the filter

   Rinse or replace cartridges, or backwash sand and DE systems per the manual. Opening with a clean filter shortens the cloudy-water phase by days.

7. Brush, skim, and vacuum

   Brush walls and steps, skim the surface, and vacuum settled debris to waste if your plumbing allows. Mechanical cleaning removes the organic load chemicals would otherwise burn through.

8. Test the water

   Test pH, total alkalinity, calcium hardness, stabilizer, and chlorine with fresh strips or a kit — spring readings drift over winter, and everything downstream depends on this baseline.

9. Balance, then shock — per product labels

   Balance in order (alkalinity, then pH, then the rest), with the label on each container as the only dosing chart. Finish with a startup shock, applied and timed as its label directs.

10. Filter until the water clears

    Run long filtration cycles and re-test daily until the water is clear and readings hold in label ranges. In cool May 31 water this usually goes quickly; warm late starts take longer.

11. Inspect for winter damage

    Walk the deck, coping, and tile line looking for new cracks, and watch the pad for drips during the first day of runtime. Catching a weep in May 31 beats a leak hunt in June.

12. Clean, dry, and store the cover

    Scrub the cover with a soft brush and mild cleaner, rinse, and let it dry fully before folding. A dry, shaded bin keeps mildew and rodents away until fall.

What to buy before the rush

Every item below sells out somewhere in Montana every June. Stocking the short list before the rush costs nothing extra and saves the mid-project store run — the chemicals guide explains what each category actually does.

• Pool opening chemical kit

  Skips five separate purchases; sized by gallons on the box.

• 7-way test strips

  The opening baseline: pH, alkalinity, hardness, stabilizer, chlorine in seconds.

• Start-up shock

  Label-dosed oxidizer that sets sanitizer control while water is still cold.

• Filter cartridge / DE refill

  Swap or refresh at opening while everything is already apart.

• Leaf net + wall brush

  The debris you remove by hand is chemistry you keep.

• Robotic pool cleaner

  It scrubs the floor overnight; you sleep through the worst chore.

How Missoula compares locally

Before booking a service slot, compare Missoula against its neighbors: Coeur d'Alene (142 mi) models to June 1, Spokane Valley (160 mi) to May 23, against Missoula's own June 7 — placing it in the earlier half statewide at the 50th percentile. When autumn planning starts, the closing checklist picks up where this page ends, and the Missoula pool season page holds the one-glance summary.

The measuring stick here is Missoula 2 NE — 3.0 miles to the northeast, elevation about 3420 feet. Its 1991–2020 record is what the model reads for Missoula; your backyard in Missoula County will run a touch warmer or cooler with shade, wind, and pavement, which is exactly the slack the two-week lead absorbs.

Field notes for Missoula owners

Water level: where spring rain helps and hurts

Aim for mid-skimmer. Low water lets the pump gulp air and lose prime; high water makes the skimmer door lazy so surface debris stays put. Spring storms will move the level around — recheck after every serious rain during the opening weeks.

Cartridge, sand, or DE — the opening difference

Cartridges want a hose-down (or replacement if pleats are fraying); sand wants a long backwash and a check that the bed hasn't channeled; DE wants a backwash plus a fresh label-measured coat. Whichever you run, start the season clean — a filter opened dirty turns the clearing phase from days into a week.

Mesh vs solid covers at opening

Mesh covers let fine silt and nutrient-rich meltwater through all winter, so mesh-covered pools typically open cloudier and slightly greener — budget an extra day of filtration. Solid covers open cleaner but hand you a swamp on top to pump off first. Both work; they just fail differently.

Making a 57-day season feel longer

The normals give Missoula roughly 57 true warm-swim days, so the margins are the strategy: an on-time opening adds usable cool-water weeks up front, a solar cover adds degrees at both ends, and a heater turns the shoulder months from theoretical to Tuesday-night real.