For people who intend to climb Mount Shasta at some point:

 https://www.shastaavalanche.org/weather/forecasts/current-summitplateau

This URL gives you present and expected temperatures for the summit of Mt. Shasta. However, in 1970 I climbed the mountain to the summit in August with 3 friends and it was about 30 degrees on top with 100 mph winds that nearly blew me down. Luckily, the winds were constant instead of gusty(gusty 100 mph winds are likely to kill you on a summit by the way) so I was okay because I could just lean into the wind and mostly be okay and luckily no snow or ice was blowing on the summit that day. 

Mt. Shasta is considered either the easiest hard climb in California or the hardest easy climb in California.

Several people die every year climbing it because they don't have enough experience at high altitudes because physiologically you and everything around you is different. I found a seagull at around 13,000 feet on Mt. Shasta totally freaked out because the air was too thin to fly in for him. So, I chased him off a cliff where he fell about 100 feet before he could get enough air under his wings to fly again. So, if I hadn't chased him off a cliff he might have died up there at that altitude.

So, if a seagull can't fly up there what is it going to do to you? This might be an important question to ask before you ascend to the summit.

Note: The way people often survive gusty 100 mph or more winds on a climb is to rope together. The main problem with this is if one person falls you all might also fall too unless you are aware when one person falls. You only have about 1/2 second to brace when someone falls who is tied to you by the way. After that the momentum is going to take everyone on the rope down the mountain. Something to think about.