Weather values are instantaneous:
#CFHT/GEMINI Weather Tower Data
2009/11/23 14:59:19 #Date/time of acquisition
WS=   17.18   #Wind speed (knots)
WD=   37.18   #Wind direction (degrees) (0-360)
T =    7.33   #Temperature (degrees celsius)
RH=    8.65   #Relative humidity
BP=  615.65   #Barometric pressure (millibars)