Every year an estimated 10,000 humpback whales migrate from Alaska to Maui to mate and give birth. Humpbacks begin arriving in Maui in early December, with numbers peaking from January through March.
Haleakala Crater is within the national park. Go for Sunrise or Sunset. (see link below for permit fees) Cycling Crater Road is one of the most popular tours in Maui. They will drive you to the top of the volcano and let you coast your way down by bike. Here is a list of some tours: https://www.mauiinformationguide.com/maui-bike-tours-comparison.php Many suggest choosing a company that provides some warm gear, in the winter there is snow at the summit. For more info read: https://www.mauiresortrentals.com/blog/visiting-haleakala