Based on available literature, we collected and presented in tables the values of optimal precipitation (for some field-cultivated vegetables) which are still sometimes used in Poland. We also included a short summary of how they are defined and how the necessary corrections are introduced. Included optimal precipitation values have been developed by: Dzieżycet al., Grabarczyk, Klatt and Press. Therefore, it is possible to define (estimate) precipitation deficits for specific species of vegetables depending on the temperature or soil weight classification (light, medium, heavy) in various regions of Poland. By recognising optimal precipitation, we can plan, design or introduce irrigation and manage it. The formulas developed by Grabarczyk offer an additional possibility of calculating expected average increase (growth) of vegetable crops as a result of irrigation within various precipitation zones in Poland.