If you live in the U.S., the age of consent may be 16, 17, or 18, with possibly corresponding 'close-in-age exceptions'. Check the legal age of consent for your state or country.
Make sure that you understand the consequences! If you are caught breaking these laws, you may be fined and/or sent to prison and legally labeled a sex offender. It is illegal to have sex with a minor (younger than age 16, 17, or 18 in the United States) if you are legally an adult.
It is illegal to have sex in many outdoor and public spaces.