Weather values are instantaneous:
#CFHT/GEMINI Weather Tower Data
2008/05/11 13:55:21 #Date/time of acquisition
WS=   11.33   #Wind speed (knots)
WD=   55.17   #Wind direction (degrees) (0-360)
T =    3.71   #Temperature (degrees celsius)
RH=   31.69   #Relative humidity
BP=  614.50   #Barometric pressure (millibars)