I get questions like these quite often:
"What are the predictions for June 6th through 10th for Houston/Dallas? Is there a website for future predictions?" - Julia
"I was wondering what the weather will be like for next weekend before the Memorial Holiday? I’m taking a road trip to Abilene, Texas, and I’ll be driving through Dallas, and was wondering what the weather will be like when driving through Dallas.” - Rachel
“My husband and I are celebrating our 1st anniversary over Memorial Day weekend and have a trip to Cancun booked. I checked the weather today and looks like it is going to be storming EVERY day that we are there. I am kind of freaking out and trying to decide what to do.” - Leslie
The question is: How do I make plans for a forecast beyond seven days? There isn't a comforting answer.
Weather models are pretty good three to five days out. However, there is a drastic drop in accuracy once you go beyond six days. All of these questions are asking for a forecast 9 to 20 days away, and a lot can change with the weather in that time.
Low pressure disturbances that create rain usually only show up on the weather models 12 hours to three days out. Cold fronts, especially for southeast Texas, can stall north of us or even on top of us, and that will completely change a forecast two to three days out. This explains why our seven-day forecast will change for the weekend Monday through Thursday of the same week. I could keep giving examples, but the point is: The weather is constantly in motion and always changing.
Studies have been done on long-range forecasting past seven days and found no skill in prediction. In fact, climatology, or the seasonal average, will beat a computer-generated long-range forecast.
AccuWeather is marketing a 25-day forecast. I would love a middle school school student to do their science fair project comparing the forecast to what actually happens.