Abstract: The invention relates to measuring climate inside a longitudinal cavity of a structure from two or more positions. The cavity has two ends that may be ends open to a surface of the structure, or closed ends inside the structure, or a building comprising the structure. The climate is measured by an arrangement inserted to the cavity. The arrangement comprises plurality of interconnectable sections. The sections comprise at least one sensor section and one or more extension sections. The at least one sensor section and one or more extension sections are interconnectable in a series for insertion inside the cavity. The at least one sensor section is configured to measure at least one quantity indicating the climate. The one or more extension sections are configured to position the at least one sensor section from at least one of the ends of the cavity to a measurement position within the cavity.