How much rain does a garden need?
A useful working figure for an established border in warm, dry weather is roughly 10–20 mm of rain over five days. But the honest answer depends on your soil, plants, and how much the weather has been drying the ground.
The millimetres matter less than the balance
What a garden really needs is rain that roughly matches the water the weather removes. Warm, windy days dry the soil faster than the rain replaces it, so a 15 mm shower after a dry week is not the same as 15 mm spread across a week.
Otter compares the forecast rain against the estimated drying over the same five days, which is why the same rainfall total can give different advice in different weeks.
- roughly 10–20 mm over five days for an established border in warm weather
- more for pots, hanging baskets and new planting
- less for established trees and shrubs with deep roots
- a single heavy shower is less effective than steady rain
Check the official restriction for your area. A Temporary Use Ban can change what you are allowed to do with a hosepipe, whatever this guidance says. Check your postcode.