This feature produce weather forecasts and it is also useful for other forecasts as well. You can include the influence of a planet entering a zodiac sign (ingress) or a lunation. Some astrologers consider a transiting aspect at the time that a planet enters a zodiac sign or a lunation to have an effect until the next ingress or lunation. For example, suppose that you believe it is likely to rain more than average over a two week period from New Moon to the next Full Moon if at the time of the New Moon for a given location Venus is conjunct the fourth house cusp. This is, in fact, a rule used by some astrometeorologists (astrologers who predict weather). In Sirius you can include this rule.