For summer hiking experience from Kilpisjärvi to Halti, June is too early for most years. The best time to go is July and August. Keep in mind that the nights can get rather cold by late August, possibly under zero degrees, Celsius.
"So I was sitting in my cubicle today, and I realized, ever since I started working, every single day of my life has been worse than the day before it. So that means that every single day that you see me, that's on the worst day of my life."
--Peter Gibbons (Office Space)