Understanding the weather can make sailing much more enjoyable through predicting the likely wind strengths and directions we should expect from the forecasts given. One of the most important and dramatic is when a cold front passes. The cold front is the boundary between the warm moist air and the cold dry air giving two distinct air masses. The cold air is moving faster and is heavier than the warm air and it starts to tuck under and lift it from the surface. The difference in the temperature between the two masses determines whether there will be squalls and thunderstorms or comparatively more subdued weather. Tightly packed isobars behind the cold front on the forecast indicate that the wind is likely to be strong and blustery. If the sea is warmer than the air then the evaporation from the sea gives rise to impressive cumulus clouds which in turn will give rise to squalls when it starts to rain. Preparing for these squalls by reefing the sails early or by diverting around the oncoming front will make for better sailing.