Weather values are instantaneous:
#CFHT/GEMINI Weather Tower Data
2009/11/22 20:38:12 #Date/time of acquisition
WS=    9.22   #Wind speed (knots)
WD=   44.58   #Wind direction (degrees) (0-360)
T =    0.19   #Temperature (degrees celsius)
RH=    8.65   #Relative humidity
BP=  616.45   #Barometric pressure (millibars)