I've actually been fishing Sprague Lake for over a few weeks and doing very well; the best day, my wife and I stopped fishing after we each caught three a piece with her 26" MONSTER and my 21" "Biggy" making the other large trout look almost small.
This morning, I arrived before dawn to find 7 cars in the lot and most of the bank spots already taken. However, today I was fishing "Solo"; so I was able to find a spot. I quit by 0830 HRS with 4 fish of about 17" - 18". With the Heat Wave, the Sprague Lake bloom is ON and I suspect, the eating quality of the fish will be on a rapid down swing. If you go; go early and clean your fish ASAP and get them on ice. As a side note, all but one of my fish, really slammed the bait and only with a quick grab, was I able to save my rod from going into the lake.