The below does not constitute legal advice, does not form an attorney-client relationship, and should not be relied upon to take or refrain from taking any action.
The short answer is yes. Assuming you're not viewing from a legitimate website that would have the movies legally, even if you don't "download" them, you are still making a temporary copy while you view it on your computer. This is a violation of copyright law.
The potential costs of this kind of thing are immense. Just a few weeks ago an individual was held liable for nearly $2 million for infringing the copyright in just 24 songs. You can be on the hook for up to $150,000 per movie if you are found to willfully infringe. It simply isn't worth it. Just pay the $10 or so to see the movie in the theater.
Yes, even if you don't save a copy to your hard drive, you're copying and performing someone else's copyrighted movie without permission. The chances of getting caught are low, but as has been pointed out, the stakes and penalties are high.
Disclaimer: Please note that this answer does not constitute legal advice, and should not be relied on, since each state has different laws, each situation is fact specific, and it is impossible to evaluate a legal problem without a comprehensive consultation and review of all the facts and documents at issue. This answer does not create an attorney-client relationship.