Winter is the season of extremes not Summer

With all the heat of the past month around Charlotte and the talk of extreme weather. I thought I’d take a look at when we really do get our extreme weather in the Charlotte area. I already knew when this was but when you look at the actual numbers there are quite revealing. In this case I’m going to be talking just about temperatures and their extremes or in this case record highs and lows.

To compared extremes in high and low temperatures I looked at the “average/normal/typical” highs and lows for our 2 opposite months. Those 2 months are July, the hottest month of the year on average and January, the coldest month on average of the year.

Winter January

Below you see how the average highs and lows along with the average record highs and lows compare. I then show the average spread between what is average to what the record would be for that date. So you can see in January for us to break a record high or low. We typically have to be 24° warmer or colder than the average temperature for a given date. Remember these are averages for the month and some days may be more or less

January

Averages: High: 51° Low: 30°

Average Records: High: 75° Low: 6°

Average spread: High: 24° Lo: 24°

Summer July

Just like in winter above; below I look at the month of July typically the hottest month of the year in Charlotte, NC. You can see when we break a record high or low in the summer it may only be 10-13° above or below what is typical. In fact one day not too long ago on July 26th the record low was just 60° when the average low is 68°. Pretty amazing to see how close normal actually is to extreme for that date at least.

July

Averages: High: 89° Low: 68°

Average Records: High: 102° Low: 56°

Average Spread: High: 13° Low: 12°

This chart below visualizes the difference in winter and summer pretty well. Some of the data is off our all-time record high is 104° not 103°. You can see clearly how the spread in extremes versus normal is from winter to summer. (Curtsey weatherspark.com)

    So why is this?

The reason this happens is 2 fold.

#1 We just have more weather in the winter than summer. The Jetstream is much more active in the winter and thus the storm track is more active over us. This means storm systems move over the area just about every other day. You get lots of wild swings in temperatures and weather.

#2 In the winter the air is drier meaning less water vapor or humidity. Dry air has a low heat capacity which means it can cool and heat up rapidly. In the summer we have a pretty stable amount of humidity all summer long. This humidity doesn’t allow for a lot of change in temperature. Our proximity to the Atlantic Ocean and the effect of the Bermuda ridge keeps our weather pretty stable and humid. This is why when we do get dry air in the summer, i.e. drought, we also end up with very extreme heat 100° +.

So as I illustrated we actually get our most extreme temperature changes during the cooler parts of the year. Some of the most extreme cases are in February and March. During the summer are whether typically is pretty stable. If you want to see a hot summer remove the humidity if you want a cool summer give us plenty of rain and clouds. It really is that simple.