Why temperature matters
Concrete does not dry. It hardens through a chemical reaction between cement and water, and that reaction is sensitive to temperature.
- Below 40°F. The reaction slows to a crawl. A freeze in the first day or two can weaken the slab for good.
- 50 to 75°F. Ideal. The concrete gains strength steadily and the crew has time to finish it properly.
- Above 85°F. The surface can dry faster than the concrete sets. Crews pour at dawn and keep it damp.
The season, month by month
- Best
- Good
- Works, with care
- Ground thawing
- Most crews stop
- March to mid-April. Frost is leaving the ground and the soil is soft. Tear-outs can start, but concrete never goes on frozen or saturated ground.
- Late April to August. Good pouring weather. May and June are the busiest, and hot days mean early-morning pours.
- September to mid-October. Often the best conditions of the year: mild days, cool nights and a little less demand.
- Late October to winter. Workable while nights stay above freezing. After that, most residential crews stop until spring.
The catch with late fall
New concrete is at its most vulnerable to deicing salt in its first winter. The usual guidance is to give it about a month of drying after curing before salt touches it. A driveway poured in early November gets that month if you keep salt off it yourself, but you cannot stop the street's slush from riding in on your tires. If you pour late, plan to rinse the apron on mild days and read our first-winter care guide.
When to ask for estimates
For a spring driveway, ask in February or March. Contractors build their spring schedule over the winter, and the first warm week brings a flood of calls. People who already have a signed estimate get poured in April and May. People who call in May are often looking at July.
For a fall pour, ask by August. If your project needs a permit or an association's approval, add a few weeks for that.
Does it matter if it rains?
Light rain a few hours after finishing does little harm, and damp weather in the following days helps curing. Heavy rain during the pour or the finishing is the problem, because it washes cement out of the surface. A careful contractor watches the forecast and will move your date before risking it. That is a good sign, not a nuisance.
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