Weather values are instantaneous:
#CFHT/GEMINI Weather Tower Data
2009/11/22 13:38:27 #Date/time of acquisition
WS=    3.61   #Wind speed (knots)
WD=  319.51   #Wind direction (degrees) (0-360)
T =    4.43   #Temperature (degrees celsius)
RH=   28.82   #Relative humidity
BP=  615.39   #Barometric pressure (millibars)