Clovis summers are hard on fresh concrete. Clovis Concrete Crew pours year-round, and from June through September that means following hot-weather practices that most homeowners never see but every slab depends on. This guide explains what happens to concrete in the heat, what a good crew does about it, and what you can ask before pour day.
How Hot It Gets Here
Records for Fresno, right next door, show about 38 days a year at 100 degrees or more and 113 days at 90 degrees or more. The 100 degree window typically runs from early June to mid-September, and summer skies are nearly cloudless. Low humidity and afternoon wind add to it.
What Heat Does to Fresh Concrete
The National Ready Mixed Concrete Association's Concrete in Practice sheet CIP 12, Hot Weather Concreting, summarizes the problem using the American Concrete Institute's hot-weather guide, ACI 305R. "Hot weather" isn't only temperature. It's any combination of high air temperature, high concrete temperature, low relative humidity, high wind, and solar radiation that speeds up moisture loss and cement hydration. Clovis summer afternoons check every box.
According to CIP 12, those conditions cause:
- Higher water demand. Hot concrete needs more water to stay workable, and extra water means lower strength and durability.
- Faster setting. Concrete sets quicker, so finishing has to happen faster.
- Plastic shrinkage cracking. Fast evaporation dries the surface before the concrete sets, opening shallow cracks.
- Thermal cracking. A slab poured on a hot day followed by a cooler night can crack from the temperature swing.
- Lower long-term strength. Concrete cured at high temperatures early on ends up weaker later than the same concrete cured near 70 degrees.
What a Good Crew Does in Summer
These practices come from CIP 12's hot-weather rules, plus how we apply them on Clovis jobs.
1. Pour early
CIP 12 advises avoiding the hottest part of the day for placing and finishing. Our summer pours usually start at first light so the finishing is done before the heat builds.
2. Dampen the subgrade and forms
On hot, dry days, CIP 12 recommends dampening the subgrade, forms, and reinforcement before placing concrete, without letting water pond. Dry, hot base rock pulls water out of the bottom of the slab.
3. Adjust the mix
Ready-mix suppliers can add water-reducing and set-retarding admixtures to keep concrete workable longer in heat. CIP 12 also notes that synthetic fibers can help reduce plastic shrinkage cracking. For larger or hotter jobs, suppliers can cool the mix with chilled water or ice.
4. Don't add water on site
CIP 12 says not to exceed the mix's designed water, and to avoid adding water to concrete more than 1 1/2 hours old. Watering down a stiff load on a hot morning is a common shortcut, and it weakens the slab. It also warns against sprinkling water on the surface to make finishing easier.
5. Control evaporation
When low humidity and wind are in the forecast, CIP 12 lists windbreaks, sunscreens, fog misting, and evaporation retarders to reduce plastic shrinkage cracking. An evaporation retarder is a spray film applied between finishing passes to slow moisture loss from the surface.
6. Have enough hands
Fast-setting concrete needs a crew big enough to place, finish, and cure on time, and deliveries spaced so trucks can unload immediately.
7. Cure right away, and keep curing
CIP 12 calls for curing as soon as finishing is done and continuing for at least 3 days, using wet burlap and plastic, a liquid membrane curing compound, or water curing. It notes that white-pigmented curing compounds reflect heat from the surface. Skipping curing is the most common reason Valley slabs come out dusty, weak on top, or cracked.
8. Cut joints on time
Control joints are tooled or saw-cut as soon as the concrete can take it without raveling. In summer that window comes early, so the saw crew has to be ready.
What You Can Do as the Homeowner
- Ask what time the pour starts. In July, a noon pour is a red flag.
- Ask how it will be cured, and for how long.
- Ask about joints: layout, and when they'll be cut.
- Keep sprinklers off the new slab unless we tell you otherwise, and keep pets, kids, and cars off until we say it's ready.
- Follow the curing plan. If we leave the slab covered or ask you to keep it damp, it matters.
Winter Is Easier, Mostly
Clovis winters are mild. Freezing mornings happen sporadically, mostly from mid-December into late January, and tule fog can slow drying. A cold snap is a reason to protect a fresh pour overnight, not to stop work. Spring and fall remain the easiest seasons to pour.