In late May, weather could be anything from baking heat to snow. So pack sensibly!

Bass Lake Weather

The current weather where we're camping:

Forecast: Looks like it's going to be Sunny and high-70s in the daytime over the weekeend and low-50s at night. We would recommend a minimum 2-season sleeping bag and some blankets.
10-day Bass Lake Weather Forecast

Yosemite Weather

The current weather in Yosemite National Park (note that after 2pm, the low temperature is displayed):

Forecast: Looks like it's going to be Mostly Sunny and high-60s over the weekend. There may be some showers on Sunday so bring a raincoat! This obviously varies greatly based on altitude. You'll want layered clothing suitable for both warm and cool weather.
10-day Yosemite Weather Forecast