Moisture that forms on the room-side glass or frame during cold weather, especially after cooking or showering, may be condensation: warm, damp indoor air is meeting a cold surface. Water or fog trapped between panes points instead to a failed sealed glass unit. A rain leak is more likely when staining or dampness appears around the window opening during or after rain, but the visible spot may be some distance from where water entered.
Wipe up moisture to limit damage, then note which side of the glass is wet and when the problem occurs. Take photos, record the weather and indoor conditions, and tell the property manager if the window is in a strata building. Persistent staining, soft materials or repeated wetting calls for an assessment of the window and adjoining wall details. Canyon's building envelope service covers windows, flashings and moisture-related exterior repairs.