Warm season vegetables need a lot of heat and at least 6- 8 hours of full sun to grow well. The seed needs a soil temperature of 21-32 degrees C just to germinate.
Knowing what planting zone you live in will help you research what will grow best in your garden.
If you live in a cooler climate It is best not to start these vegetables seeds outdoors too early or they may rot or will not even germinate. This is a waste of your seeds. Wait until your soil is warm enough. In the northern hemisphere this is usually not until late May or early June.
You want a good stretch of warm temperatures ( a week or so) before planting either seeds or transplants outdoors so the soil will be warm enough.
A good rule of thumb - If you feel it would be warm enough to comfortably walk in your garden barefoot, it is a good time to plant these vegetables.
Rather than starting these plants by seed, most often they are started indoors and transplanted out. This gives the gardener more control over making sure the seeds germinate well and it gives the plant the length of time it needs to grow really well. Warm loving plants are most often purchased from nurseries or garden centers.
One example is a tomato plant which needs 16-20 weeks to produce and ripen it's fruit. In a northern climate if you start a seed in late May or early June there is not enough time for that plant to produce before the frost may hit in late September.
By starting the seeds indoors in late February, the plant has 3 months to grow before being transplanted to your garden. This gives the plant a better chance of giving you ripened tomatoes in July and August. By the time the frost can hit you have already had a great harvest.
Squash, cucumber, peppers, and eggplant are similar in their growing requirements.
These vegetables also do very well in containers on a balcony or even in your front or back garden. One main benefit of growing warm season vegetables in containers is you can move the container to get the most sun possible especially if your garden is mostly in the shade.
For more information on any specific vegetable please go to my vegetable list. Here you will find useful information for planting, growing and harvesting each veggie.