I have done it without grow lights in Southern California but it is more challenging. I carried seed trays in and out each day. However I had problems with damping off. If there is no sun and it is cool it's a recipe for damping off.
I still carry my seed trays in and out from time of germination but tomorrow and the next day they will remain indoors under the grow lights due to cold and rainy conditions.
Also the seedlings get better growth with the longer grow light / sunlight combined conditions. They get a few hours of light before being carried outdoors and several more hours after being brought indoors.
I try to make sure they get at least good midday sun.
I use full spectrum standard screw in grow light bulbs. I have several wattages and cone angles hung from strings above which I can adjust up and down using the clamp on fixtures.
Right now they are indoors but will be going out in about twenty minutes and stay there until about five o'clock.
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