I'm growing some from seed this year as opposed to just the sweet green version.

It can withstand  sun most of the day but (providing it is hydrated accordingly), like you say, there may be an issue with the wind somehow dehydrating or damaging the leaves.

Not sure if it is an option, but you might want to try alternating a few days behind glass and outdoors. If it is wind then you should see it perk up.

I only managed to grow basil successfully for the first time this year, I've kept it indoors on a sunny windowsill, I water every other day and feed it once a month, it's flourishing. This isn't purple basil though, where abouts are you in the world? I'm in the UK and I've never managed to grow basil outdoors successfully. I would try moving it indoors and see if that helps 

Hey everyone, thanks for your replies.
So, this is the only herb I've ever had problems with. Normally my only problem is eating them quickly enough! Especially my other basils- they always grow super super quick.
To answer some of your questions, I did plant in a potting mix, in a plastic pot, with good drainage. I've tried alternating behind glass and outdoors. I haven't been watering it too much, but (I forgot to mention this before) it has been very rainy here and the soil has been kept quite moist.  It's also been somewhat cool since i planted - mid teens to twenties (celcius). (I'm in Canada) Which I don't think is THAT cool for these plants, but as I mentioned, I've never grown purple basil before and am uncertain of it's hardiness. All my other herbs are growing like crazy already (except the mint, which is a little strange since normally the mint is a monster grower)
Thanks everone for your advice. I moved it again two days ago. Will see how it fairs and let you all know.

I have been granted(??) a red basil plant by a friend but never used it yet ........I must get aquaited with it first ............I'm so shy with new plants   

good morning Joy it's six a.m here and I'm going to water my orto