A boat is not household contents
Watercraft carry severe limits on a homeowners form, often a few thousand dollars and frequently with liability excluded entirely once the boat is in use. A separate watercraft policy covers the hull, the liability and the people aboard, and in a town organized around a lake that is not an optional refinement.
Heat as a continuous load on the building
Sustained extreme heat shortens the service life of roofing, sealants, HVAC and anything made of plastic. It is wear rather than a sudden event, and wear is excluded. What matters is whether the sudden failure that follows is settled at replacement cost or depreciated.
Months with nobody in the house
A second home standing empty is a different risk and often a different policy. Vacancy provisions can restrict losses past a stated period, and unattended damage runs far longer before anyone notices. Say so when the policy is written, because this is readily accommodated in advance and not at all afterwards.