Weather values are instantaneous:
#CFHT/GEMINI Weather Tower Data
2009/11/07 11:07:38 #Date/time of acquisition
WS=    1.97   #Wind speed (knots)
WD=  254.80   #Wind direction (degrees) (0-360)
T =    7.43   #Temperature (degrees celsius)
RH=   24.52   #Relative humidity
BP=  618.28   #Barometric pressure (millibars)