Vegetables are classified as warm or cool season vegetables. The terms refer to the best growing time for the veggies. While you can grow both in the same garden, cool season veggies are typically grown in the spring and fall, while warm season vegetables are grown during the heat of the summer.
Cool Season Vegetables
Cool season vegetables, like peas, onions and lettuce, prefer cool soil and cool to moderate growing temperatures. These vegetables can be planted early in the spring as soon as the soil can be worked. Some cool season vegetables, such as lettuce 'bolt' during warm weather.
Warm Season Vegetables
Warm season vegetables, such as cucumbers, tomatoes and peppers, prefer warm weather and must be planted after the danger of frost has passed. These vegetables thrive in the heat of summer and suffer when nighttime temperatures drop below 50 degrees Fahrenheit.