When Is the Best Time
This is probably a year-round hike but only as long as the weather is decent. The best time with the least rainfall is from mid-April till the end of May. It can be a bit crowded during summertime. I would recommend going in the afternoon to experience a memorable sunset on the way back (of course when the sun is out:-))
For detailed weather and crowds information check out my article from Stac Pollaidh one of the Assynt Hills.
Best Months to Visit
Location and Tips
Coire Lagan is a fine place on the Isle of Skye. It is situated in the southern part of the famous Cuillin ridge. The loch is surrounded by three Munros - Sgurr Alasdair, Sgurr Dearg and Sgurr Mhic Choinnich. The path to the loch starts at Glen Brittle campsite and is in excellent condition; the only "hard" part is near the loch where you have to walk a little bit above scree and do an easy scramble. It is suitable almost for everyone. There is crystal clear water in the loch, and the views down the Coire towards Loch Brittle are just amazing. The round trip to the loch and back takes around 3 hours—more information about the hike.