The cool, dry season offers the best window for vegetable production in the tropics, assuming an adequate water supply. Pest and disease pressures are relatively low and temperatures are moderate. By contrast, the rainy season brings a combination of high temperatures and humidity that encourages the return of voracious snails and other pests. This means that many desirable vegetables, such as lettuce and tomatoes, are difficult to produce under rainy season conditions without significant inputs such as plastic row covers and pesticides.