The earliest a METAR observation can be coded is what time?

The correct timeframe for coding a METAR observation is 30 minutes past the hour. This standard aligns with the operational practices established for aviation weather reporting. METAR reports are typically generated on a regular schedule, specifically at every hour and half-hour past the hour. However, reporting can begin at what is typically the 30-minute mark to ensure all necessary meteorological data is collected and verified for accuracy before transmission. This allows for a comprehensive assessment of the weather conditions, providing pertinent information to aviation professionals.

The 15 and 25-minute options do not adhere to this standardized timing system for METAR observations, while the 45-minute option is also not correct as it falls outside of the established reporting intervals. Understanding this hourly cadence is essential for familiarizing oneself with the timing of METAR reports and their significance in ensuring safety and operational efficiency in aviation.