Weather values are instantaneous:
#CFHT/GEMINI Weather Tower Data
2009/11/23 21:21:07 #Date/time of acquisition
WS=   19.53   #Wind speed (knots)
WD=   45.99   #Wind direction (degrees) (0-360)
T =    2.70   #Temperature (degrees celsius)
RH=    7.49   #Relative humidity
BP=  617.29   #Barometric pressure (millibars)