Methods, systems, and apparatus for monitoring humidity at a property are disclosed. A monitoring system performs operations including: obtaining, from multiple humidity sensors within the property, humidity data; obtaining occupancy data that indicates whether people are within the property; determining, based on the humidity data and the occupancy data, that humidity in a first area of the property changed more relative to a change in humidity in a second area of the property during a time period when no person was present in the first area and no person was present in the second area; and in response to determining that humidity in the first area changed more relative to a change in humidity in a second area of the property during the time period, providing an indication of a water leak in the first area of the property to a user.