Hi! My name is XXXXX XXXXX I am glad to assist you. For your question, may I know if there is specific occasion that you will be attending to? How long will you be staying there?
Hi! Unless you are going there for the purpose of attending convention and professional reason, you can bring casual jeans, t-shirts depends on gender, shorts and light sweatshirt. I suggest you also bring toiletries and medical supplies though stores are all over the place for things you may have forgotten. You may also bring photo equipment ( digital or regular camera ). If you are planning to go camping/outdoor gear, please do not forget to bring towel, swimsuit, sunglasses and hat.
I pulled up the 10 day forecast for San Jose, CA. It looks like the weather is going to be in the mid 70's to low 80's during the day time and in the evening dropping down into the mid 50's. The humidity is in the 35% range which means you will not feel the heat as bad as if the humidity was higher.
I would take a sweater or jacket for the evening in case it is cool for you and the day time temps. seem very pleasant with a slight chance of rain. This is a link for the 10 day weather forecast: http://www.weather.com/weather/tenday/San+Jose+CA+95113
Depending how you feel about the temps you will be able to judge on weather you will need long or short pants and whether you need long or short sleeve shirts. I personally find the evenings a bit chilly, so I would pack long pants and jacket for 50* weather. The day time temps are very pleasant, so the choice would be what you feel like wearing. Overall you will want to pack clothes for the cooler evenings and comfortable daytime temps.
I hope this helps you to pack for your trip.