Weather values are instantaneous:
#CFHT/GEMINI Weather Tower Data
2009/07/03 17:54:30 #Date/time of acquisition
WS=   10.52   #Wind speed (knots)
WD=  275.40   #Wind direction (degrees) (0-360)
T =    5.64   #Temperature (degrees celsius)
RH=   15.75   #Relative humidity
BP=  617.60   #Barometric pressure (millibars)