Most cool season crops sprout very fast, do plan a week or so from seed to seedling.
Then most of the Cole crops can grow and get to a good size in their container for a couple of months (given the right size container, or transplant from small seed pots into perhaps a 4" pot).
Most greens (lettuce etc) however need to go into the ground right away.
Root crops are direct seeded, not started in the house. Most are mature in 1-2 months (radish, turnip) or take longer (Onion, garlic, leek) so you will have to read the package on these.
I would do this:
Check the climate for the following:
When does the day or night temperature drop, in the fall? Most of these crops are not going to be at their best in the summer heat. You can start the seeds just in time to plant them out as the summer heat is dying.
You can try pushing the season, getting the seeds started a bit early, then planting the crops where they will be shaded from the hot afternoon sun. (Add hoops and shade cloth over these rows) See if they are worth doing, or if the flavor or texture is bad. Then you will know for next year which are OK to get started early.
When is the first frost expected? Most cool season crops do not mind the early light frosts, so go ahead and start seeds for plants that might be halfway to harvest by this date.
How fast does it go from 'first frost' to 'freezing'? If the crops are still producing you can put up some hoops and clear plastic and keep them going somewhat into the 'freezing' weather. Try it, see which crops handle this and which do not.
Best way to try it is something like this:
Select some crops that grow pretty fast, like lettuce.
Plant a few feet worth of seed every couple of weeks, maybe once a month.
Think about what the weather will be like over the next 2 months, and plant the seeds accordingly.
During the late spring and up to mid summer, plant lettuce varieties that are heat tolerant, and perhaps plant them in a bit of shade.
Late summer and into the fall, when you know it will be milder plant the more delicate varieties that cannot tolerate the summer heat.
Keep on planting them into the fall, until you know it will be snowing. Hoops can protect that last crop under average fall-to-winter conditions. But if winter comes suddenly and too fast, then you might lose that last crop. It is a gamble, but worth it.
Start again in the late winter, perhaps even starting seed indoors until the soil can be worked. Then use the hoops to support clear plastic, and get a jump start on the season.
Keep track of how each variety performs for you, especially if it bolts to seed under certain conditions. Then you would know to try that variety at a different time of year.
Just a suggestion, If you go to www.rareseeds.com they actually sell a clydes garden planner and is well worth the $3.00 I believe it is. They also have some great seeds for sale.
It is called Clyde's Garden Planner, and it has spring indoor and outdoor sowing, fall indoor and outdoor sowing. For fall you set your last frost date and it will tell you when to start the seeds, and the spring set your last frost date in spring and it will give you set of dates...