Seasonal Lag: What is it and why does it occur?

Water, it’s a vast resource across the Earth and it plays a huge role not only in keeping us alive, but in warming the Earth’s atmosphere. We are now well into July here in Mid-Missouri and although today was a pleasant day, the thermometer is on the rise. One would think that when summer officially starts in June, that we would experience our hottest days of the year, but we don’t. The answer to why lies in the properties of water.

Water covers nearly three quarters of the Earth’s surface, and it’s this water that creates what is called seasonal lag. Seasonal lag is where you experience the hottest and coldest days of the year well after the official start of each season. Why does this occur? Imagine if you will placing a pot of water on the stove and heating it up, it doesn’t automatically get hot, in fact it takes a good 10 to 15 minutes before the water even begins boiling. The amount of energy that is required to heat the surface of the water is greater than what it takes to heat the land.

Water plays a major role in distributing heat across the globe, whether it be through hurricanes or thunderstorms. It’s for this reason that we see a delay in heating of the Earth’s oceans that we experience our hottest days of the year, and why our electric bills rise well after summer has started.

ABC 17 reached out to Boone County Electric to provide data of the months with the highest electric costs. Boone County electric gave us a sample of 1700 households from 2015. In that data it shows that the months of July and August experience the greatest amount of electricity usage, which can be attributed to increase usage of air conditioning.

So what does this mean for you? Well, you can expect to shell out a few more bucks to keep your house cool during the next few weeks as an upper level ridge builds into the area. The closer you are to a massive body of water (oceans), the longer you can expect to experience summer carrying on into the fall months. It’s for this very same reason that the coldest days of the year are experienced well after winter has started because it takes water longer to cool off than land. As mentioned, the Earth’s oceans not only hold the majority of the sun’s radiation, but it also helps to distribute heat around the globe, in what is called seasonal lag.