Fair weather and Weather condition

Fair weather noun - Moderate weather; suitable for outdoor activities.

Weather condition and fair weather are semantically related. In some cases you can use "Weather condition" instead a noun phrase "Fair weather".

Weather condition noun - The atmospheric conditions that comprise the state of the atmosphere in terms of temperature and wind and clouds and precipitation.

Fair weather and weather condition are semantically related. Sometimes you can replace phrase "Fair weather" with "Weather condition", this phrases are similar.