Well variation is going to be true in any climate in this country, (unless you live in Southern California or Florida), this is because the country lies in between three distinct air masses: the Continental Polar air mass which originates in Canada (cP for short), the Maritime Tropical air mass which originates over the southern Atlantic and the Gulf of Mexico (mT) and the Maritime Polar air mass which originates over the in the Northern Atlantic and Pacific (mP). There is a fourth air mass present mostly during the summer months, but it does not affect our area at all.
So what do these air masses have to do with temperature variation? These air masses have certain qualities to them that resemble their source region or where the climate of which they came from. So when they move into a region of the country, it takes on the characteristics of that region. It can be seen today with the cP air mass moving southward as it normally does in winter. It is bringing frigid arctic air and winds that blow from the north as this air mass descends across the Midwest and Mid-Atlantic. It can also be observed easily in the summer when the mT air mass moves northward causing higher temperatures and humidity and eventually the summer afternoon thundershowers.
The interactions of these air masses are only one part of the equation here though. It is also known that temperature is more variable in winter rather than summer. This is due to the presence of relatively drier air. The lack of vapor in the air makes air temperature more variable and higher temperature swings more likely to happen.
Also the ground plays a huge role in temperature variability. That is actually because factors like soil depth and precipitation. Soil depth can have dramatic effects on the ground’s heat capacity, which can affect how quickly the earth warms or cools in an area. Added to that, precipitation makes this heat capacity and thermal conductivity (transfer of heat within the ground) higher for soil and sand, thus stabilizing the temperature.
The variation of temperatures can be seen better the farther north of the tropics one travels. This is largely due to the vast differences in the amount of sun radiation that area receives in winter than in summer. The state with the largest variability in temperature surprisingly enough is Montana. This is due to being under the influence the infamous ‘Chinook’ winds, which can raise or lower temperatures rapidly from one extreme to another in quick succession.
People point to global warming as a main factor for changing temperatures and more extreme weather events. The IPCC report projects that regional temperatures and precipitation will rise 10-20% within the next 50-100 years. These findings though are found to have low confidence and large room for uncertainty and error.
When comparing temperature findings for statewide temperature trends since 1896-today, there was not an overall warming trend at all.
Climate change and global warming does in fact have a negative effect on temperature variability. In the most recent journal of Climatic Research, it was shown that temperature anomalies were on a downward trend with the rising global temperature.
George Mason University’s own Dr. James Kinter aids caution for looking at weather event and pointing to climate change as the answer. “We have to be really careful to make sure people understand that a climate forecast is not like a weather forecast. It’s a prediction of how the probabilities will change rather than a prediction of a particular amount of rainfall or a particular temperature.”
So where does that leave us? Here in Fairfax, we actually have quite moderated and controlled climate on both a smaller day-to-day scale and on a larger year-to-year scale. This means our seasons are fairly regular with a predictable trend of temperatures.
-James
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