The probability that your vote will affect the outcome is only one way of looking at the situation. There are a number of other reasons why you should go out and vote, even if you live in a safe seat/state.
You can find arguments for voting in safe seats all over the place. Why am I being asked to vote
Arguments on Voting counts are based on UK numbers, but the same follows in most places.
In 2017 there were 14.5m non voters, that’s more potential votes than any one party received. If all of these people went to the polling station, then the outcome could be very different – even in constituencies seen as ‘safe’.
In 2016 in California if everyone who didn't vote had turned up and voted Trump, then Trump would have won. Actually it's worse than that. If all those votes had turned out and voted for me, then I would have won. Which would lead to some tricky eligibility questions...
Turnout 58.74%
Nominee Votes Percentage
Hillary Clinton 8,753,788 61.73%
Donald Trump 4,483,810 31.62%
Did Note Vote 9,298,320 (70% of number of people who voted)
Turnout 58.74%
Nominee Votes Percentage
Hillary Clinton 8,753,788 61.73%
Donald Trump 4,483,810 31.62%
Did Note Vote 9,298,320 (70% of number of people who voted)
There's an LSE blog post with 5 reasons. Again the details are UK, but the principles apply across the world. I've just cribbed the headers, follow the link to the full piece.
1: The seat might not be as safe as you think
2: To influence your MP’s behaviour
3: To make future elections more (or less) competitive
4: To influence national vote share
5: To help keep democracy alive