WorkWindow

Concrete Pouring Weather in St. Louis, MO: 10-Day Windows & Best Months

St. Louis gives you roughly 149 workable concrete pouring days a year, concentrated April through October. The single best month is August, averaging 23 days that clear every check — highs of 87°F, lows near 67°F, and a 24% daily rain chance. Below: the live 10-day check and St. Louis's full month-by-month table.

GOOD — a clean label day MARGINAL — one borderline check NO — hard fail or stacked flags

The rules this check uses

Typical bagged-mix requirements for small DIY pours, scored against St. Louis's forecast above. The 48-hour freeze rule dominates every other row; structural work follows engineer/ACI specs instead of this table.

Typical label thresholds for concrete pouring — the ruleset behind every St. Louis verdict above.
CheckThresholdWhy it matters
Air temperature 40–90°F — ideal 50–85°F DIY pours work from 40–90°F; 50–85°F is the sweet spot.
Overnight low ≥40°F during the first 48 h A low under 40°F inside the first 48 hours puts you in cold-weather concreting — not a DIY window.
Dry before no soaking (≥1.0") in the prior 24 h What fell before you start matters as much as what falls after — surfaces hold water invisibly.
Dry after <0.1" rain for 6 h after (12 h light rain after finishing still risks surface marks) The make-or-break window: rain here undoes the work, not just delays it.
Wind ≤20 mph (rapid surface drying up to 28 mph) Scored on the windiest working hour; the marginal band changes the method, not the day.

Always follow your product label — formulas vary. Treat the table as the consensus range across brands — the label in your hand is the final word.

Best months for concrete pouring in St. Louis

How St. Louis months rank: temperature-rule days minus NOAA rain odds, from 1991–2020 normals. An estimate for planning, not a forecast.
MonthAvg highAvg lowRain odds/dayWorkable days 
January 41°F 22°F 29% 0
February 46°F 26°F 28% 0
March 56°F 35°F 33% 0
April 68°F 45°F 39% 18
May 76°F 56°F 40% 19
June 85°F 65°F 34% 20
July 88°F 69°F 27% 23
August 87°F 67°F 24% 23
September 80°F 59°F 24% 23
October 70°F 46°F 27% 23
November 56°F 35°F 28% 1
December 45°F 27°F 30% 0

Figure 149 workable days a year in St. Louis, spread across April through October. Shoulder months turn on the overnight rule: an afternoon at 68°F passes, but the 40°F night floor is what actually opens the season in April. Neighboring towns shift by a month or more — the Missouri comparison shows where St. Louis sits.

Sealing the same driveway later? Sealcoating in St. Louis wants warmer nights (50°F+) than the pour did.

Climatology here is measured at Cahokia, Il Us (8.9 km away). Treat the monthly numbers as the neighborhood average; a shaded north-side deck runs colder and damper than any of them. The exact formula lives in the methodology.

St. Louis by the numbers

Prep checklist

  1. Clear the 48-hour rule first: two nights over 40°F. April opens that door in St. Louis; January (22°F average lows) slams it.
  2. Stage everything before mixing: forms braced, base compacted and damp, tools rinsed, help booked.
  3. Cut plastic sheeting and weight it at the pour's edge — St. Louis sees rain on 24% of August days, and the 6-hour rule doesn't negotiate.
  4. Resist the watery mix: it finishes easier today and dusts forever after. Low slump wins.
  5. Work the sequence: screed on the sheen, float as it dulls, and leave bleed water alone.
  6. Edge and joint with an edger + float set — control joints every 2–3 slab-thicknesses in feet.
  7. Hold the moisture in (sheeting or misting); when October nights dip toward 46°F, a curing blanket is the difference.
  8. Traffic schedule: feet at 24–48 hours, tires near day 7. Anything structural runs on engineer/ACI specs, not this checklist.

Gear that saves a window

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FAQ

What temperature is too cold to pour concrete?

The line is a 40°F low inside the first 48 hours; an actual freeze (32°F) physically damages young concrete. St. Louis's January nights average 22°F — firmly out — while August nights hold near 67°F. Small pours only; structural work follows engineer/ACI specs.

Can you pour concrete before rain?

The engine wants 6 protected hours; light rain later actually feeds the cure. With 40% rain-day odds in May versus 24% in September, St. Louis's dry-season pours barely think about this rule and wet-season pours live by the radar. For small DIY pours; structural schedules follow ACI.

How long does concrete need to be protected from freezing?

Keep it above freezing for at least the first 48 hours (the engine calls any sub-40°F low in that window a NO). In St. Louis that rules out roughly January-adjacent months entirely and makes shoulder-season pours a two-night forecast decision. DIY scope; anything structural follows engineer/ACI cold-weather practice.

Is it OK to pour concrete in hot weather?

To a 90°F high, yes — with shade, cool mix water, a damp subgrade, and a dawn start. Above 90°F the surface sets while the core is plastic and shrinkage cracks map the slab. St. Louis averages 0 such days in July — rarely the binding constraint here.

How long before you can drive on new concrete?

A week before tires, 24–48 hours before feet — at August-typical St. Louis temperatures (87°F highs). When nights slide toward 22°F, add days: cure speed is temperature. Early loads print permanent marks; the bag's cure table wins every argument.

Best season for concrete work in St. Louis?

April through october — the months with 40°F+ nights, sub-90°F days, and manageable rain. August leads at 23 workable days; January bottoms out near 0.

Other projects in St. Louis

Concrete Pouring nearby

Guides

Climatology: NOAA 1991–2020 normals via CAHOKIA, IL US (8.9 km from St. Louis center, elevation 400 ft); live outlook by Open-Meteo.