Cicadellids (Homoptera: Cicadellidae) are occasional pests of vineyards in temperate areas, and unchecked populations can build up to high densities to cause leaf burn followed by defoliation and yield loss. Therefore, an optimal sampling scheme would allow determination of risk at minimal cost. Because the development of leafhopper nymphs and feeding injury is closely tied to temperature, a model driven by the accumulation of degree-days was developed to predict leafhopper cumulative abundance at 5, 50, and 95% levels in vineyards. The model was based on 22 data sets collected over 7 yr in three vineyards in southern Quebec. It was based on the cumulative abundance of nymphs of the eastern grape leafhopper; the grapevine leafhopper; the threebanded leafhopper; the Virginia creeper leafhopper; and Erythroneura vitifex Fitch. The lower threshold temperature for development was 8°C. Paired t-tests and the forecasting efficiency confirmed the validity of the model. The model indicated that monitoring for leafhoppers in vineyards should be initiated at 630 DD (5% cumulative abundance) and terminated at 1,140 DD (95% cumulative abundance). Maximum abundance would be between 850 and 860 DD (50% cumulative abundance) calculated from 1 March.