The time for sowing depends upon where you live. What to plant depends upon the season and weather.
Vegetables are generally divided into two categories: cool-season crops and warm-season crops.
Cool-season crops should be planted so that they mature when the weather is cool, either in spring or early summer or in autumn or winter. Cool-season crops come to harvest in cool weather, either in spring or fall or winter. Cool-season crops can be planted when the soil and air tempertures are cool, as low as 40 º F (5 º C) . Mature cool-season crops can survive in temperatures near freezing without protection. Cool-season crops do not do well in the warmest summer temperatures.
Warm-season crops should be planted so that they mature when the weather is warm, when the soil and air temperatures are above 50 º F (10 º C). They will grow best when the temperature is 75 º F (24 º C) or warmer. Warm-season vegetables can be grown out of their season if they are protected from temperatures below 50 º F (10 º C).