How often should one water plants is often determined by rainfall.
Check your local forecast for the week ahead on one of the many Weather Forecast sites on the internet?
To get your local weather forecast for the week ahead simply pop your postcode or place name into the designated spot on the Weather Forecast site e.g. here.
On seeing the forecast you might find this eliminates the need to water outdoor beds and borders at all that week, but not containerised plants!
These will still require regular manual watering.
If watering is required it is better to water well rather than often!
If too little water is applied, this will only moisten the upper layers of the soil and it will not get down to the root system where it is needed, necessitating further watering a short time after.
If in doubt, check the moisture levels by digging a hole adjacent to the plant/s with a trowel / spade to see how far the water has percolated down.
Watering in the evening allows the water to drain deep into the soil / compost over night, and early morning watering should be done before the heat of the sun builds up and causes evaporation.
If practical, move potted plants into the shade to protect from the sun until they recover.
Throw a sheet of fleece over those pots that can’t be moved.
Always water to an area consistent with the plants optimum spread, watering outwith this area will encourage weeds and create a moist surface that is suited to slugs and snails.