Minimum Temperature to Pour Concrete: ACI 306 and State DOT Rules

Short answer: ACI sets no single minimum air temperature for pouring. ACI 306R-16 applies cold-weather practices once air is, or is expected to be, below 40°F during the protection period. Concrete should then be placed and kept at 55°F or more for sections under 12 inches, or 50°F for 12 to 36 inches. Many state DOTs add an air cutoff.

That is the gap this page closes. ACI tells you what temperature the concrete needs. State DOT specs, project specs and local practice decide when you're allowed to place it and how long you must protect it. Below are the ACI numbers, then ten state DOT specs side by side, each checked against the spec book edition named.

When does cold-weather concreting start?

Under ACI 306R-16, it starts when the air temperature "has fallen to, or is expected to fall below, 40°F (4°C) during the protection period." The protection period is the time recommended to keep the concrete from being harmed by the cold. ACI's 2023 curing specification, ACI SPEC-308.1-23, uses the same 40°F definition.

Older documents use a different test. ACI 306.1-90 (reapproved 2002), the reference specification a project spec can cite for cold-weather work, defines cold weather as "a period when for more than three successive days the average daily outdoor temperature drops below 40°F." It ends the cold period when temperatures above 50°F occur during more than half of any 24 hours. NRMCA's CIP 27 uses that older wording too.

The two can disagree. A single 30°F night after warm days is cold weather under ACI 306R-16 but not under ACI 306.1-90. Plan to the newer, stricter definition unless your contract says otherwise.

What temperature does the concrete need to be?

ACI 306R-16 Table 5.1 sets minimum concrete temperatures by section size. Thin sections need warmer concrete because they lose heat faster.

For heavier sections, NRMCA's CIP 27 gives 45°F as placed for 36 to 72 inches. MassDOT's 2026 table, which uses the same thickness bands, goes down to 40°F for sections over 6 feet.

Warmer is not better beyond a point. ACI 306R-16 section 4.3 says placement temperature should not exceed the Table 5.1 value by more than 20°F. NRMCA explains why: hotter concrete needs more water, loses slump faster and cracks more easily.

These are concrete temperatures, measured to ASTM C1064. The air can be well below freezing while the concrete is at 55°F, if it arrives warm and is insulated.

How long must cold-weather concrete be protected?

At minimum, until it reaches about 500 psi. ACI 306R-16 section 3.2 says concrete protected until it reaches at least 500 psi "will not be damaged by exposure to a single freezing-and-thawing cycle." At 50°F, most well-proportioned mixes reach that within 48 hours.

ACI 306R-16 Table 7.2 then sets the protection period, at the Line 1 temperatures above:

For elevated slabs, beams and girders, ACI 306R-16 section 8.1 says these minimums do not allow enough strength gain. Base protection and form removal on in-place strength.

Why it matters: NRMCA says the potential strength of concrete that freezes fresh "can be reduced by more than 50%," and it won't be durable. Concrete that will see repeated freeze-thaw cycles while saturated should reach about 3,500 psi first. The day-by-day detail is in how long to keep blankets on new concrete, and the overnight risk is covered in will concrete freeze overnight at 28 degrees.

How do state DOT cold-weather specs compare?

DOT specs turn ACI's guidance into hard rules, and they don't agree with each other. The table covers ten states whose spec books we checked section by section; the edition is in brackets. Each state links to its full answer page.

Three patterns stand out:

• Triggers range from 35°F to 45°F, and two states use the calendar. Ohio starts at 36°F, New York and Illinois structures at 45°F. Minnesota and Illinois also switch on protection by date, whatever the weather.
• Protection is longer than ACI's minimum. Ohio requires 5 days, Washington, North Dakota and New York 7, and Illinois holds protection on structures until the concrete is 7 days old. MassDOT requires full design strength.
• Several measure the concrete surface, not the air. Minnesota, Ohio and North Dakota all set a surface temperature range for the protection period.

More states are covered on our answer pages: Alabama, Alaska, Arizona, Arkansas, California, Colorado, Connecticut, Florida, Georgia, Idaho, Kansas, Kentucky, Louisiana, Maine, Maryland, Mississippi, Missouri, Montana, Nebraska, Nevada, New Hampshire, New Jersey, North Carolina, Oklahoma, Oregon, Pennsylvania, Rhode Island, South Carolina, South Dakota, Texas, Vermont, Virginia, West Virginia and Wyoming. Each cites its spec section.

What should a cold-weather concreting plan include?

Many DOT specs in the table want a written plan before the first cold pour, and ACI 306.1 lists what it should cover. Its submittal checklist names:

• procedures for protecting the subgrade from frost, and keeping ice and snow off reinforcement and forms before placement
• methods for temperature protection during placement
• the types of covering, insulation, housing or heating to be provided
• curing methods during and after the protection period
• use of strength-accelerating admixtures
• methods for verifying in-place strength
• procedures for measuring and recording concrete temperatures
• procedures for preventing drying in dry, windy conditions

ACI 306.1 section 1.5.1 adds one more: what you will do if the weather changes abruptly or equipment fails. A heater that quits at 2 a.m. is the usual case.

Several DOTs make the plan a hold point. Minnesota, North Dakota, Washington and Massachusetts all require the engineer to accept the plan before concrete is placed, and Illinois requires one for pavement when the forecast low is below 17°F. On private work, the project specification decides. Writing it down is still worth doing, because it forces the heater, blanket and testing decisions before the truck arrives.

Can you pour concrete in freezing weather?

Yes, if the concrete is protected. ACI 306R-16 even notes an upside: concrete placed cold, protected from freezing and properly cured "has the potential to develop higher ultimate strength" and greater durability than concrete placed warm, with less thermal cracking.

What you can't do is pour on frozen ground. Building codes and DOT specs forbid it. ACI 306.1 explains that a frozen subgrade can freeze the new concrete, or let the foundation settle when it thaws. The rules and thaw method are in can you pour footings on frozen ground.

Cold-weather pour checklist

1. Hold a pre-pour meeting. ACI 306R-16 section 4.1 recommends the GC, concrete contractor, supplier, testing lab and owner agree the cold-weather methods ahead of time. For bridge decks placed between October 1 and April 1, NYSDOT 557-3.06 says the preplacement meeting should also review cold-weather operations.
2. Get protection on site first. ACI 306.1 section 2.1 requires all protection materials and equipment on site before cold-weather concreting starts.
3. Clear and warm contact surfaces. Remove snow, ice and frost from subgrade, forms and steel. ACI 306.1 says massive metal embedments below 32°F will damage the concrete cast around them.
4. Order the right concrete temperature from Table 5.1 above, and tell the producer the section size.
5. Heat water and aggregates, not cement. WisDOT 502.3.9.2 prohibits heating cement. IDOT 1020.14 bans frozen aggregates.
6. Use accelerators for speed, not as antifreeze. NRMCA says accelerating admixtures "do not prevent concrete from freezing." It limits calcium chloride to 2% by weight of cement and recommends non-chloride accelerators where corrosion of steel is a concern. WisDOT forbids salt or other chemicals added to prevent freezing.
7. Cover as soon as the surface allows and protect corners and edges first. ACI 306R-16 section 4.4 says they are the most vulnerable.
8. Record temperatures. ACI 306.1's checklist sets a floor of twice every 24 hours. Record the air temperature, the concrete temperature as placed, and the weather.
9. Look after the test cylinders. NRMCA, citing ASTM C31, says to cure them at 60 to 80°F for the first 24 to 48 hours in an insulated box with a min/max thermometer.
10. End protection gradually. Stay within the Line 5 drop above, or the spec's rate. WisDOT allows 5°F per hour and 40°F per 24 hours, Ohio 20°F per 24 hours.

What about heaters and enclosures?

Vent them. ACI 306R-16 defines carbon monoxide as a gas from fossil-fuel heaters that "can cause dusting of concrete surfaces that are less than 24 hours of age." MnDOT 2401.3G.5 requires heated enclosures to be vented to prevent carbon dioxide buildup. WisDOT 502.3.9.3 requires exposed surfaces inside heated housing to be protected from drying and carbonation. Unvented heaters in an enclosure are also a serious risk to the crew. Our toolbox talk on propane heaters and carbon monoxide covers the OSHA side.

How do you cure concrete in cold weather?

Keep the moisture in, but don't add water. ACI 306R-16 section 3.2 recommends "little or no external supply of moisture" during cold-weather curing, except inside heated enclosures. Water curing can leave the concrete critically saturated when protection comes off, which lowers its freeze-thaw resistance. NRMCA recommends curing compounds, impervious paper or plastic sheets instead. MnDOT 2401.3G suspends conventional wet curing if the forecast shows temperatures below 32°F within 24 hours.

Cold also delays form removal. NRMCA's rule of thumb is that a 20°F drop in concrete temperature roughly doubles setting time. See when can you remove concrete forms for stripping criteria by spec.

Asking on site

When the forecast turns, the crew's question is usually "are we OK to pour tomorrow?" Ask Verika "can we pour the wall tomorrow, low of 26 tonight?" and it answers from ACI 306R-16, the DOT spec for your state and your company's own cold-weather procedure, citing each one. If none of them covers the case, it says so. You can start a free trial and load your own cold-weather plan.

ACI guides are recommendations unless your contract makes them mandatory. Spec editions change, and the project specification, engineer of record or local building official has the final say.

Sources

1. ACI 306R-16, Guide to Cold Weather Concreting (preview: sections 1.1–4.4) — American Concrete Institute, 2016
2. ACI 306R-16 excerpt (sections 8.1–9.2; Tables 7.2, 8.8) — American Concrete Institute, 2016
3. ACI 306.1-90 (Reapproved 2002), Standard Specification for Cold Weather Concreting, preview — American Concrete Institute
4. ACI SPEC-308.1-23, external curing specification, preview (section 1.3) — American Concrete Institute, 2023
5. Cold Weather Concrete, reproducing ACI 306R-16 Tables 5.1 and 7.2 — Cemstone, 2024
6. CIP 27, Cold Weather Concreting — NRMCA
7. WisDOT Standard Specifications 2025, Section 502 and Section 415 — Wisconsin DOT
8. MnDOT Standard Specifications for Construction, 2025 Edition (2301.3M.3, 2401.3G) — Minnesota DOT
9. MDOT 2020 Standard Specifications for Construction (602.03.T, 706.03.J) — Michigan DOT
10. ODOT Construction and Material Specifications, 2023 (online version 07/17/2026), 511.12 — Ohio DOT
11. NYSDOT Standard Specifications (USC), January 1, 2026, Vol. 2 (555-3.04, 555-3.08, 557-3.06) — New York State DOT
12. Iowa DOT Standard Specifications, Series 2023 (2403.03 F) — Iowa DOT
13. IDOT Standard Specifications for Road and Bridge Construction, adopted January 1, 2022 (Arts. 1020.13, 1020.14) — Illinois DOT
14. MassDOT Standard Specifications for Highways and Bridges, 2026 Edition, Division II (901.33) — Massachusetts DOT
15. NDDOT Standard Specifications for Road and Bridge Construction, adopted July 1, 2025 (602.04) — North Dakota DOT
16. WSDOT Standard Specifications for Road, Bridge, and Municipal Construction, M 41-10, 2027 (1-01.3, 6-02.3(6)A2) — Washington State DOT