Concrete pour weather
Can I pour tomorrow?
Check your site free. We read tomorrow’s forecast every way a pour gets ruined (frost that stops it curing, a hot, dry, windy spell that cracks it, and rain that washes it out), and give you one straight call.
How it works
- 1
Tell us your site
Your postcode and what you're pouring: concrete, mortar, screed or render. Thirty seconds.
- 2
We read the weather
Every way a pour gets ruined: cold that stops it curing, hot dry windy spells that crack the surface, and rain that washes it out.
- 3
You get a straight answer
A clear go / caution / no-go for tomorrow, with the numbers and what to do to protect it.
One call. The pour saved.
Get it wrong on the weather and the bill lands three ways. Knowing the night before whether to pour, protect, or stand down pays for itself the first time it saves you a load.
Rip-out & re-pour
A ruined slab
A frosted or cracked pour means rip-out and re-pour. Thousands gone, plus the delay.
Cancelled load
A wasted load
Ready-mix is ordered the day before and costs to cancel once it's batched and rolling.
Idle gang + plant
A stood-down gang
A gang stood down for the morning, with the plant on hire, is money straight out the door.
Good to know
Can I pour concrete in cold weather?
As a rule, don't place concrete below about 5°C and falling, and never let a fresh pour freeze in roughly the first 24 hours. Ice in the mix wrecks the strength and you're looking at a rip-out and re-pour. If it's borderline, you can still pour with insulated blankets or a heated enclosure holding it above freezing until it has set. CanIPour flags an overnight low at or below 4°C as a caution (that's ACI 306R's cold-weather-concreting trigger) and at or below freezing as a no-go.
What temperature is too hot to pour concrete?
Heat itself is less about a single number and more about how fast water leaves the surface. Above roughly 30°C a pour goes off quickly, so you lose workability and risk cold joints; above about 35°C it's usually a no-go. The bigger summer risk is plastic-shrinkage cracking, driven by the evaporation rate (hot, dry and windy together), not temperature alone.
How does wind and humidity crack a fresh pour?
Wind and low humidity pull water out of the green surface faster than bleed water can rise to replace it, and the surface cracks as it shrinks. The recognised measure is the ACI 305 evaporation rate: at or above about 1.0 kg/m²/h the risk is high and precautions are essential, and 0.5 to 1.0 calls for windbreaks, an evaporation retarder and covering the pour as soon as you can. CanIPour computes this rate from the forecast temperature, humidity and wind.
Can I pour if it's going to rain?
Light rain after the surface has taken its initial set is usually fine, but rain on a fresh, unworked pour washes out the cement, raises the water/cement ratio and leaves a weak, dusty finish. Have sheeting ready and aim to finish and cover before rain arrives; a real downpour during placing is a no-go.
Does it work for mortar, screed and render too?
They're more cold- and wet-sensitive than mass concrete. Bricklaying mortar and cement render shouldn't go on much below 3°C and falling and must be protected from frost; interior screed shouldn't get wet at all. CanIPour uses tighter cold and rain limits for mortar, screed and render, so the same forecast can read fine for a slab but caution for render.
Is CanIPour a guarantee it's safe to pour?
No. It's decision-support from the weather forecast, and it leans cautious on purpose because a wrong 'go' is the expensive mistake. Treat it as the night-before sense check before you order the load and book the gang, and always read your own site on the day.
Built on recognised standards
- BS EN 13670
- ACI 306R
- ACI 305
- NHBC
- BDA
CanIPour's thresholds follow this published guidance. It's decision-support, not certification or endorsement by these bodies. Forecast by Open-Meteo.
The check is free. The text alert is the paid bit.
Don’t want to remember to check?
Register your sites and CanIPour watches them for you: the evening go/no-go by text and email, before you commit the load and the crew. We’re building it with UK groundworkers; tell us where you pour and we’ll let you know the moment it’s live.