Planning a 7-10 trip either mid June or mid September. June is wildflower season, but also mosquito season, right? June has later sunsets than September. What other factors should I consider and which is the better time of the year for long day hikes?

Of those two I'd choose mid June. My favorite time to go for hikes is mid May, when there's more snow runoff and far fewer visitors, but spring is still springing in early and mid June. The main problem is that, by then, Tahoe is already starting to look like it does on July 4th, at least most years. It depends on when the first major warmups are during late spring. The same is true for mosquito swarms btw.

I think both would be great, although I personally prefer July and August. Where will you be hiking? I highly recommend the Shirley Lake hike at Squaw Valley, Five Lakes near Alpine, Mt. Judah near Sugar Bowl, and others. We usually do 5-6 miles.

Probably staying in South Lake Tahoe, but want to hike wherever we can get a great 5-10 mile moderate rated day hike. Still debating which is a bigger advantage, less crowds and less mosquitoes in fall or more daylight/wildflowers in mid June.

Oh, also Emerald Bay (DL Bliss State Park) on the west shore and Spooner Lake (part of the Tahoe Rim Trail) on the east.