Our department has been examining the water turnover and the water demand of tomato and the impact of water supply and temperature on yield for 35 years. Comparing to the results of temperature and precipitation conditions during vegetation, we considered that we can qualify the years according to weather, which vary sharply in expected yield and water demand. A new method has been developed for the evaluation and the adaptation of investigational results of irrigation on tomato during our experimental series from 1962. Data of cumulative daily mean temperatures and precipitation (+ irrigation) after plantation are well representing the water household conditions of plant-growth development and crop-forming. In the view of temperature yield can be concluded from water supply. From the viewpoint of yield/ha, dry material content of yield, average weight of fruits and soluble dry material content of fruits (% Brix), the effect of water supply is characteristic and differ from each other. The optimal parameters of yield are formed by different water supplies according to temperature. The optimal water supply dynamics makes the determination of water demand and the estimation of irrigation effects possible. The introduced method gives guidelines to the irrigation of tomato, depending on the aim and conditions of production. According to the determined connections that are based on weather details, beside more exact timing of tomato irrigation, we can also estimate the quantity and quality of yield.