How warm is Westchester getting?

UntitledSince 1900, the rate of change in mean annual temperature for the Hudson Valley has been 1 degree Fahrenheit per 100 years (source: NOAA NCDC, New York, Climate Division 5
, Temperature:
December-November 1896-2012).

That sounds pretty minor. But it is not.  Most of the warming has been in the most recent decades.

Since 1980, the Hudson Valley has seen the mean average annual temperature climb about 2 °F, from just under 44°F to just over 46°F (based on the linear trend line).  (See Figure 1.) Again, that may not sound like a lot. But let’s look deeper.

A more revealing trend is what is happening to the mean maximum temperature: How it is warm, how hot does it get?

Specifically, let’s look at Westchester County, which is under the influence of the urban heat effect from New York City and home to nearly 1 million Hudson Valley residents.

The linear trend line for mean maximum temperature shows whopping 4°F climb from just under 82 °F to just under 86°F from 2000 through 2012 for Westchester. (See Figure 2. Source)

As you know, warm air can hold and transport more moisture than cold air. So, are we are getting wetter, with more precipitation, as we get warmer?

Yes, and no. The answer depends on how many years you count.

Since 2000, Westchester County has seen an actual slight dip in the sum total of annual precipitation. But the maximum precipitation events in any given year have varied wildly in that time (as we all know from droughts in 2009 to Irene to Lee in 2011 to Sandy in 2012).

However, since 1900, the Hudson Valley has seen a dramatic gain of about 7 more inches of rain to 2012. The linear trend line for annual precipitation climbs from 38 to about 46 inches. For more great details, visit the terrific Mohonk Preserve Daniel Smiley Research Center.

What does this mean? While we may need slightly less heat in the coming winters, we’ll be using much more air conditioning with each passing year.

Time to weatherize and insulate our homes and businesses. The caulk and insulation that helps keep us warm in the winter will also keep us cooler in the summer.

Note: The weather history sources are provided here so you may do your own research. Trend lines are simplistic tool in analyzing the complex patterns of weather (what you get) and climate (what you expect to get). So my apologies in advance to all my climate science friends for oversimplifying!

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