There were daily afternoon rain showers during the Memorial Day weekend in the Sierra, which included thunder and lightning on Saturday just to keep things interesting for all the campers. Hiking at 9,000 feet elevation will include traipsing through snowbanks. It’s still solid snow at 10,000 feet and above.
SIERRA SNOW REPORT FOR HIKERS: As of last weekend (May 28-30), there were snowdrifts on the trails above 9,000 feet. A pretty solid snowpack should be expected at 10,000 feet and above, lakes will still be partially frozen, and the mountain passes could be treacherous, especially early in the morning.
Pay attention to your creek-crossings. Water levels in the mountains will be lower in the morning and higher in the afternoon. Especially keep this in mind if doing an out-and-back dayhike; what was crossed easily on the way out could be impassable on the way back.
Although the hot weather will have the Sierra foothills and Central Valley sweltering this weekend, backpackers with an upcoming entry date will certainly appreciate the acceleration in snowmelt caused by the warmup in temperatures.
In Three Rivers, river levels are peaking at midnight, which is how long it takes that day's snowmelt (about seven hours) to travel down the river canyons to 1,000 feet or so elevation.