It is very important to understand that not all weather stations report every 15 minutes or even every hour. Although some - often located at international airports - report every 30 minutes, others, however, only report every six hours. By international convention those are called synoptic stations or simply SYNOP's.

Because of the way in which the data are collected some data may be several hours old. Every synop station only reports at the standard synoptic hours of 00:00, 06:00, 12:00, and 18:00 GMT (also known as UT (universal time) or "Zulu" time. Most stations also make observations at the intermediate synoptic times of 03:00, 09:00, 15:00 and 21:00 GMT.

However, these hours were introduced before the days of the internet and modern telecommunication. It always took some time to have the data read and coded by an observer, who phoned or faxed it to the national weather service and from there to the international users. In recent years automaticaly reporting stations became more and more widespread and thus - maybe in only a few years from now - we might see real time readings and the weather as it happens.

Current Weather are the observable conditions such as rain or snow. In the absence of any significant weather, the amount of clouds reported determine such phrases as clear or cloudy. Only stations from the Metar/Surface Air Observations network provide this information.