I generally use weatherunderground.com
They are pretty good for anywhere in the U.S. and have links to similar sites in many other countries as well.
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If you can get access to aviation weather forecasts, try to learn to decipher them. Most places you will photograph have an airport nearby so you can use the forecasts for the airport. Here I can get a 12 hourly forecast as well as a more accurate 3 hourly forecast. Example:
TAF YMES 030500Z 030618
30012KT 9999 SCT030
FM10 30005KT 9999 SCT030
PROB30 INTER 0610 VRB30KT 3000 TSRA SCT010 SCT030CB
RMK FM06 MOD TURB BLW 5000FT TILL 12
T 20 16 14 13 Q 997 999 1001 1001
Basically this means that it will be quite nice until about 1600 local where there is a 30% probability of thunderstorms. I find these forecasts much more detailed and accurate than normal weather forecasts as they give you times things will happen as well as such events as fog, haze, snow, sleet, hail, dust, smoke etc etc.