Check with your state's Extension Service. Each county should have it's own Cooperative Extension Office which provides free publications and information for the asking. They will have valuable vegetable/gardening tables available specifically for your area determined by universities and horticultural research scientists who have collected data from growing those crops in your state. Your tax dollars are already paying for this service so you may as well get some use out of it.

See how detailed these examples are:

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Vegetable Planting and Planning Calendar for Missouri (download the pdf) complete with spring and fall planting dates (underneath the spring planting dates for appropriate crops), how much to plant per person, etc. They can also tell you the average last frost date for your area and ideal planting times for specific crops and varieties in your area.

Here is an excerpt:
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Timjc,

What I have done with success is, after planting the seeds, to cover them with burlap which I then keep moist until the seeds sprout and I remove the burlap. Keeping the seeds moist until sprouting seems the key here and without some sort of covering they will dry out in this weather. Whether or not the carrots are bitter may depend, I think, on when you harvest them. If you plant to harvest in the fall, when the carrots have gained some size, the cooler temperatures -- especially after a frost -- will make them sweet.

Also what you can do is plant them close to a plant that will help to keep them cool...say along side a row of beans....I always believe this...It's worth the cost of a pack of seeds to try...here in TX I grow carrots all summer long...