Keep watering flowering plants
Don’t stop watering late-flowering plants, such as cannas. Very little rain gets through to the soil where the foliage canopy is dense so a regular top up with a watering can is really worth doing and will reward you by lengthening flowering time.
Also keep an eye on spring flowering shrubs such as camellias and rhododendrons, as these will soon begin to develop flower buds for next year. These can drop off in a dry autumn and ruin the spring display, so keep them well watered.