When temperatures rise and your lawn is competing with heat, wind, and long dry spells, your watering routine needs to shift. Summer brings a completely different set of challenges — faster evaporation, hydrophobic soil, and the constant battle between heat stress and fungus.
This guide breaks down exactly how to water your lawn in summer so it stays green, healthy, and stress-free.
Why Summer Watering Is Different
Summer changes everything:
- Heat speeds up evaporation — water disappears before it reaches the roots.
- Wind dries soil from the top down, especially in exposed backyards.
- Hydrophobic soil forms when ground bakes dry, causing water to run off instead of soaking in.
- Warm, humid nights increase fungal risk.
- Long dry spells cause shallow roots, making lawns stress faster.
You can use the same watering system year-round — but not the same watering rules.
How Much Water Your Lawn Needs in Summer
Most NZ lawns need 25–30mm per week in normal weather. During hot, dry summer stretches, that can increase to 30–40mm, depending on your:
- Grass type
- Soil type
- Wind/sun exposure
- Recent rainfall
Cool-season grasses (Ryegrass, Fine Fescue)
- Prefer consistent moisture
- Show stress quickly
- Aim for 30–35mm/week
Warm-season grasses (Kikuyu, Couch)
- More heat tolerant
- Can go longer between waterings
- Aim for 25–30mm/week
Tip: Add rainfall + watering together. If you get 12mm of rain, you only need to top up 18–20mm.
How Often to Water in Summer
Forget the one-size-fits-all approach — summer requires flexibility.
General guideline:
- 2 deep waterings per week
- 3 deep waterings during extreme heat (28°C+ over several days)
What counts as “deep watering”?
- Enough to soak soil 15–20cm deep
- Usually 15–30 mins depending on your sprinkler
- Use a rain gauge or container to measure output
Spot-watering might also be needed:
- Dry patches
- Slopes
- Edges
- High-traffic or high-sun areas
The Best Time of Day to Water in Summer
Early morning — 6am to 10am
Why it works:
- Less evaporation
- Healthier root development
- Lower fungal pressure
- Better water pressure in many homes
Avoid:
- Midday — too much evaporation
- Evening — grass sits damp overnight → fungus thrives
If mornings aren’t possible, late afternoon (4–6pm) is OK only if the grass will dry before sunset.
Smart Summer Watering Techniques
1. Use the Cycle–Soak Method
Great for hard, dry, or hydrophobic soil.
Example:
- Water 5–7 minutes
- Pause 20–30 minutes
- Water again 5–7 minutes
This reduces runoff and gets water deeper into the root zone.
2. Break Up Hydrophobic Soil
If water beads on top or won’t soak in:
- Use a core aerator to pull plugs and create channels for water
- Apply a wetting agent (soil surfactant)
- Use short, repeated soak cycles
A dry patch often isn’t your sprinkler — it’s the soil repelling water.
3. Adjust Zones for Sun vs Shade
Sunny areas dry out faster. Shaded areas keep moisture longer. Match your watering times to the conditions, not just the timer.
4. Don’t Chase Perfection
In peak summer heat, even a well-watered lawn may look slightly stressed. Aim for “healthy and coping,” not “golf-course perfect.”
Common Summer Watering Mistakes
Mistake 1: Watering every day
Creates shallow roots → worse stress in heat.
Mistake 2: Watering too lightly
Only wets the topsoil.
Mistake 3: Watering at night
Creates a perfect environment for fungus.
Mistake 4: Overcorrecting bone-dry soil
Blasting water on dry, baked earth leads to runoff. Use Cycle–Soak + aeration.
Mistake 5: Ignoring the wind
Wind can steal up to 50% of your water.
Summer Troubleshooting Guide
Heat Stress
Looks like: Crispy tips, greyish tone, footprints staying visible
Fix: Deep water + check sun-heavy areas + consider a surfactant
Dry Patches / Hot Spots
Looks like: Localised brown areas
Fix: Spot-water + core aerate + check sprinkler coverage
Fungus
Looks like: Circular patches, red tinges, odd colouring despite moisture
Fix: Reduce evening moisture + consider LAWNZ Shield fungicide
Water Runoff
Looks like: Water flowing away instead of soaking
Fix: Cycle–Soak + aeration + reduce watering speed
Quick Summer Watering Checklist
- Water 2–3 times/week, deeply
- Aim for 30–40mm weekly during heatwaves
- Water early morning
- Use Cycle–Soak on hot or compacted soil
- Treat hydrophobic soil early
- Adjust zones for sun vs shade
- Watch for summer fungus