In reality, July is the best time. Indeed now, they are being seen daily and multiple pods and multiple sites at that. Early June however offers the chance of late migrants and great breeding birds as well, so early June was the chosen time.
This year, prior to our arrival, they hadn't been seen regularly since early May, so I was far from hopeful. But we were lucky. How that luck came about was due to a bunch of boring circumstances which meant instead of seeing a Walrus which had been lost on the Out Skerries, we could be over-looking the Sound of Yell at 9am on Monday the 4th June and watching 'Busta' and 64's pod and indeed continued to watch this pod for nearly 6 hours, from land and sea in the Sound. The levels of luck are several especially since usually they don't go up and down the same stretch of coast like they did that day. As I say we were lucky.