I’m an incoming senior (class of 2019) and California resident who really wants to go to a UC (UCD, UCI or UCSD)-but, my overall UC/CSU gpa is 3.65 
However, there has been a significant improvement in my gpa over my sophomore and junior years
1st semester sophomore-2.7
2nd semester sophomore-3.8
1st semester junior-4.16
2nd semester junior-4.30
As you can see, my gpa wouldn’t be that bad if not for 1st semester sophomore year.
(I’ve also taken 12 semesters of weighted courses, so not all of them count towards my overall gpa)
I am also the president of a registered 501(c)3 non-profit organization and have an ACT of 33
My question is, do I have a shot at going to the UCs I want, or is my gpa too bad?
an upward trend is great, but is there any existential circumstance you had in tenth grade first semester for your GPA to be that low? try not to make excuses in your essays, but in the additional comments section of the application, you can talk about what was going on. however, your GPA is still quite low for those UCs. You may be a match for UCR and UCM. Include some safety schools on your list which you will be happy attending.
What is your intended major? CS, Engineering, and Biology are all impacted majors at UCD, UCI, and UCSD.
I’m also a rising senior, so I’m sure others on CC with more information and experience will be happy to help.
Good luck.
Some important stats from the UC website:
Overall admit rates (not including choice of major) for Fall 2018:
UCD: 41.2%
UCI: 28.8%
UCSD: 30.2%
Admit rates for GPA range of 3.30 to 3.69 (not including choice of major) for Fall 2018:
UCD: 9.5%
UCI: 4.0%
UCSD: 4.5%
I do not mean to discourage you from applying in any way. You seem like a great student who is willing to put in their 110% and turn things around. GPA is not everything, but it is most important to the UCs. Your 33 ACT is outstanding. Your ECs are probably good too. Work on your essays and make them shine.
Yes, the UC’s do look at GPA improvement but unless you have some extenuating circumstances that can be addressed in your personal insight essays, it may be difficult to overcome that GPA deficit. UC’s first and foremost are GPA focused but your ACT score does show that you are a qualified and capable student.
As posted by @Aneem00, you can see just based on GPA alone, your chances for an acceptance are not very good however, the UC’s do review your whole application. Test scores, HS course rigor, personal insight essays and EC’s are all part of the package and your intended major can make a huge difference also.
There is no harm in applying to UCI/UCD or UCSD but consider them Reach schools. I suggest you consider UC Santa Cruz, Riverside and Merced as options for more of a Match to High Match schools. If you are a CA resident, then some of the top Cal states are good options such as SDSU, CSU Long Beach, CSU Fullerton, San Jose State, Cal Poly Pomona.
My advice is to apply widely to a variety of schools and best of luck.