Short answer
Visalia’s normal high is 93.8°F in July and 93.2°F in August (NOAA, 1991 to 2020). NRMCA says heat, sun, wind and low humidity speed evaporation and setting, raise water demand, and can cause plastic shrinkage cracks. The fix is planning: avoid the hottest hours, shade and windbreaks, fog sprays, and curing right away.
Key facts
- Visalia normal highs: 88.8°F June, 93.8°F July, 93.2°F August, 88.3°F September (NOAA normals)
- Hot weather is any mix of high air or concrete temperature, low humidity, wind and sun that harms concrete quality (NRMCA CIP 12)
- Avoid the hottest part of the day to place and finish (NRMCA CIP 12)
- Do not sprinkle water on a slab to make finishing easier (NRMCA CIP 12)
- Wind over 5 mph, low humidity and high temperature raise evaporation and plastic shrinkage risk (NRMCA CIP 5)
Visalia by month
NOAA’s 1991 to 2020 normals for the Visalia station show four months with normal highs near or above 88°F.
| Month | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Normal high | 55.3°F | 61.3°F | 66.9°F | 72.7°F | 80.6°F | 88.8°F | 93.8°F | 93.2°F | 88.3°F | 77.8°F | 64.4°F | 55.4°F |
| Normal low | 38.4°F | 41.6°F | 45.4°F | 48.6°F | 55.4°F | 61.5°F | 66.7°F | 64.9°F | 60.1°F | 52.3°F | 43.3°F | 37.9°F |
What heat does
NRMCA’s hot weather guide says high concrete temperature increases water demand, which raises the water to cement ratio and lowers strength and durability. Concrete sets faster, so finishing has to move faster. Concrete cured hot at an early age ends up weaker than the same concrete cured around 70°F.
Fast evaporation can cause plastic shrinkage cracking before the concrete sets. A hot day followed by a cool night can cause thermal cracking.
How a summer pour is planned
NRMCA’s list: use local mix adjustments such as water-reducing and set-retarding admixtures, schedule trucks so they can discharge right away, have enough crew on hand, and avoid the hottest part of the day. If conditions are critical, its plastic shrinkage guide suggests starting late in the afternoon or early evening, or early morning in very hot weather.
On site: windbreaks and sunshades, fog sprays into the air above the slab, a dampened subgrade with no standing water, and curing that starts as soon as possible. Never sprinkle water on the surface to help finishing.
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