Question

In January 2014, the “polar vortex” swept across the eastern US leading some media outlets to claim this was the “coldest weather in decades” in Baltimore between Jan 6 & Jan 8. It turns out that only 5 years prior, in 2009, Jan 15 – Jan 17 were 5 degrees colder in Baltimore than the coldest temperatures in 2014. Why did these media outlets say it was the “coldest weather in decades”? Many statisticians say that it is a mistake to look at weather temperature records the way that media outlets looked at the Baltimore "record"; why do you think they say this is a "mistake"?

Answer 1

In January 2014, the “polar vortex” swept across the eastern US leading some media outlets to claim this was the “coldest weather in decades” in Baltimore between Jan 6 & Jan 8.
But in reality only 5 years prior, in 2009, Jan 15 – Jan 17 were 5 degrees colder in Baltimore than the coldest temperatures in 2014.

According to media outlets, this decade started in 2010 and will end in 2020. From 2021 we will have a new decade.
Since the last incident occurred in the year 2009 which falls under the decade 2000-2010, hence the said it was the “coldest weather in decades”.

Many statisticians said that it is was a mistake to look at weather temperature records the way that media outlets looked at the Baltimore "record". This mistake is because according to statistics a record for decades should be a record for exactly 10 years starting from the past up to present day. For example, if we call an event to be a record for decades, that event should not have occurred in the last 10 years from the day of record. So for this weather to become the coldest weather in decades, it should be compared with the weather of the past 10 years starting from January 6 and not with the weather of days up to the beginning of January 2010.