Forecasting Rules of Thumb

A rule of thumb is a guideline that some meteorologists use to help with weather forecasts. Although not based on scientific formulas, they are more than just a guess and have some observational knowledge behind them. Click on the boxes below to see some examples.

If there is no change in air mass taking place, then the dewpoint at 5:00 pm will likely be the overnight low temperature.
The temperatures in urban areas will be warmer than rural areas due to the urban heat island effect. An Urban Heat Island refers to a metropolitan area that is warmer than the area surrounding it.
If humidity values are high at certain levels of the atmosphere, there is chance of measurable rain.