A lot of gardeners don't know their indoor seed starts are soft and not ready for the great outdoors. They need to go through a slow acclimation process to get use to the sun's ultraviolet rays, the wind and temperature fluctuations. The process is generally called 'hardening-off' and it is how it sounds. Your seed starts need a week's time to toughen up to the world in which they will be growing. They will actually be burned by the UV rays of the sun. They will be stressed by the wind and temperature changes.
When your seeds germinate indoors and break the surface they are ready for the outdoor elements but they lose that ability as they spend weeks growing 'oh so comfortably' indoors. They have to be reintroduced to Nature. I can't give you an exact way to do this but to say... slowly over a one week period. Too many factors come into play such as; plant variety, temperature, time of day, amount of sun that day, the wind and day night temperature fluctuations.
This video discusses two ways to acclimate your plants. The way I recommend is to give your seed starts time outside 2,3,4 times a week, during nonfreezing temperatures, for 15 to 30 minutes as soon as they germinate. This exposure will make for an easy transition outdoors. The benefit is they will already be 'hardened-off' and the exposure to the sun will benefit their growth. The disadvantage to this is the possibility of insects hitching a ride back into your indoor grow area. The second method is to transition them incrementally to the outdoors, slowly over time, once the reach transplant size.