During Monsoon months i.e., from June to September, additional watering of plants may not be required during this period as the soil already has excess moisture content due to rainfall. Can water requirements for landscape irrigation be excluded for the monsoon months?
The water requirement of each type of plant is different and may not be fulfilled by the rain. The intensity of monsoon and number of rainy days also vary in different regions, climate zones. For example, the mentioned statement in the question will not be true for hot and dry region and may be true for certain coastal regions. The rainfall is also becoming more erratic with climate change.
Therefore, the landscape water requirement cannot be eliminated completely in the rainy season. The calculation does take the decrease in evapo-transpiration in the monsoon season into account.