[abdulhaq]

Religious muslims don't say that the weather forecast is heresy, that would be nonsense. Perhaps someone said to you that God can change the weather to be other-than-what-was-forecast, which from the Islamic POV is simple plain sense.

Religious folk don't deny that the course of the moon can be calculated, some say that for establishing the start of the lunar month a sighting must be obtained, this is a complex issue that has nothing to do with believing or not in the predictable motions of astronomical objects.