Weather values are instantaneous:
#CFHT/GEMINI Weather Tower Data
2009/11/07 06:28:59 #Date/time of acquisition
WS=   14.03   #Wind speed (knots)
WD=   23.73   #Wind direction (degrees) (0-360)
T =    1.93   #Temperature (degrees celsius)
RH=   31.99   #Relative humidity
BP=  617.73   #Barometric pressure (millibars)