If something is tedious, it's boring. If you're anxious to get outside and enjoy the sun, even the best lecture will seem tedious.
Tedious is the adjective from tedium, which is both Latin and English for boredom. You ordinarily wouldn't use tedious for people, just things; you might say "His speeches are tedious," but usually not "He is tedious." Something that is tedious could also be called tiresome. Shakespeare's Friar Laurence says "I will be brief, for my short date of breath / Is not so long as is a tedious tale."