An estimation apparatus comprising: an acquirer configured to acquire at least first and second sets of time-sequential observation data related to presence of clouds; and a deriver configured to derive at least a first change in cloud altitude from at least a first altitude at a first time and a second altitude at a second time, the first and second times being different from each other, the first altitude and the second altitude being derived from the first set of the time-sequential observation data, and the deriver being configured to derive a second change in cloud altitude from at least a third altitude at a third time and a fourth altitude at a fourth time, the third and fourth times being different from each other, the third time being different from the first and second times, the fourth time being different from the first and second times, the third altitude and the fourth altitude being derived from the second set of the time-sequential observation data; and a determiner configured to determine a cloud developmental stage based at least in part on the first and second changes in cloud altitude, characterized in that the first time is prior to the second, third and fourth times, and the second time is prior to the third and fourth times, and the third time is prior to the fourth times, the determiner is configured to determine that the cloud developmental stage is a cloud developing stage in a case that the determiner determines that the first change is smaller by at least a first threshold than the second change, and the determiner is configured to determine that the cloud developmental stage is a cloud diminishing stage in a case that the determiner determines that the first change is greater by at least a second threshold than the second change. an acquirer configured to acquire at least first and second sets of time-sequential observation data related to presence of clouds; and a deriver configured to derive at least a first change in cloud altitude from at least a first altitude at a first time and a second altitude at a second time, the first and second times being different from each other, the first altitude and the second altitude being derived from the first set of the time-sequential observation data, and the deriver being configured to derive a second change in cloud altitude from at least a third altitude at a third time and a fourth altitude at a fourth time, the third and fourth times being different from each other, the third time being different from the first and second times, the fourth time being different from the first and second times, the third altitude and the fourth altitude being derived from the second set of the time-sequential observation data; and a determiner configured to determine a cloud developmental stage based at least in part on the first and second changes in cloud altitude, characterized in that the first time is prior to the second, third and fourth times, and the second time is prior to the third and fourth times, and the third time is prior to the fourth times, the determiner is configured to determine that the cloud developmental stage is a cloud developing stage in a case that the determiner determines that the first change is smaller by at least a first threshold than the second change, and the determiner is configured to determine that the cloud developmental stage is a cloud diminishing stage in a case that the determiner determines that the first change is greater by at least a second threshold than the second change.