Weather values are instantaneous:
#CFHT/GEMINI Weather Tower Data
2009/11/23 10:13:38 #Date/time of acquisition
WS=    8.88   #Wind speed (knots)
WD=   35.66   #Wind direction (degrees) (0-360)
T =    7.61   #Temperature (degrees celsius)
RH=    7.73   #Relative humidity
BP=  617.08   #Barometric pressure (millibars)