Photo Phriday - 2014 11 07

An older photo, but it is very "autumn" feeling. Red leaves (poison ivy) growing on a Jersey barrier.

Weather: PA vs CO

I grew up in Pennsylvania. Yay!

Then I moved to Colorado. Yay!

Since I moved west, everyone back east has been asking me about the weather out here.  Ok, mostly those who have never visited Colorado.  You see, apparently everyone on the east coast believes that Denver is high on a mountain top.  Not so!   Here's a spoiler for those who haven't visited yet: Denver's nickname is the Queen City of the Plains.  Plains?  Yes, plains.  It's flat here.  Flat in a way that my rolling-hills-of-the-mid-Atlantic-Appalachians self couldn't imagine until I first visited.  Vast and FLAT:

Looking east, past the 'burbs southeast of Denver.
At least it's not Iowa.

But if you look west:

Mountains!

Central Park off of MLK Jr Blvd

Anyway, living in the middle of a continent and above 5000', the weather patterns are certainly different than living 2 hours away from the Atlantic Ocean. So let's compare the data!

Allentown, PA

	Units	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Year
Average High	°F	36	40	50	62	72	80	85	83	75	64	53	41	62
Average Low	°F	21	23	30	40	49	59	64	62	54	42	34	25	42
Precipitation	"	3	3	3	4	4	4	5	4	5	4	3	4	45
Snowfall	"	11	11	5	1	0	0	0	0	0	0	1	6	34
Average Relative Humidity	%	69	67	64	62	66	67	68	71	73	71	71	71	68
Mean Daily Sunshine	Hours	5	6	7	7	8	9	9	8	7	7	5	4	7

Denver, CO

	Units	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Year
Average High	°F	44	46	54	61	71	82	89	86	78	65	52	43	64
Average Low	°F	19	21	27	35	44	53	59	58	49	37	26	18	37
Precipitation	"	0	0	1	2	2	2	2	2	1	1	1	1	15
Snowfall	"	7	6	10	6	1	0	0	0	1	4	9	10	53
Average Relative Humidity	%	56	56	54	51	54	52	51	52	51	51	59	59	54
Mean Daily Sunshine	Hours	7	8	8	9	9	11	11	10	9	8	7	6	9

Comparison

	City	Units	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Year
Average High	Allentown, PA	°F	36	40	50	62	72	80	85	83	75	64	53	41	62
	Denver, CO		44	46	54	61	71	82	89	86	78	65	52	43	64
Average Low	Allentown, PA	°F	21	23	30	40	49	59	64	62	54	42	34	25	42
	Denver, CO		19	21	27	35	44	53	59	58	49	37	26	18	37
Precipitation	Allentown, PA	"	3	3	3	4	4	4	5	4	5	4	3	4	45
	Denver, CO		0	0	1	2	2	2	2	2	1	1	1	1	15
Snowfall	Allentown, PA	"	11	11	5	1	0	0	0	0	0	0	1	6	34
	Denver, CO		7	6	10	6	1	0	0	0	1	4	9	10	53
Average Relative Humidity	Allentown, PA	%	69	67	64	62	66	67	68	71	73	71	71	71	68
	Denver, CO		56	56	54	51	54	52	51	52	51	51	59	59	54
Mean Daily Sunshine*	Allentown, PA	Hours	5	6	7	7	8	9	9	8	7	7	5	4	7
	Denver, CO		7	8	8	9	9	11	11	10	9	8	7	6	9

As you can see, the basic differences are:

• Average High: Allentown's average high is a few degrees cooler than Denver's average high.
• Average Low: Allentown's average low is a few degrees warmer than Denver's average low.
• Snowfall: Denver receives an average of 53" of snow per year, while Allentown only receives 34", but...
• Precipitation: Allentown receives 45" of precipitation per year, while Denver only receives 15".  
• Humidity: It's pretty dry in Denver... 54% average relative humidity for the year, with the winter being the most humid.  Allentown is at 68% average for the year.
• Sunshine: Denver is the clear winner here, with 9 sunshine hours per day (mean).

Humidity and sunshine hours are the biggest differences.  Allentown has overcast weather for much of the winter season, and is pretty humid all year.  Denver's winters are much more sunny (though both cities are at nearly the same latitude), and is generally not very humid at all.  Denver's general lack of humidity contributes to that 53" of snow melting into less than 15" of water.  Spring and summer rainstorms in PA can last a week, whereas July in Denver brings the daily 30-minute thunderstorms, followed by clear skies and sunshine.

Notes

Allentown's temperature/precipitation/snowfall measurements were taken at Lehigh Valley International Airport (1981-2010).  This is pretty much in the center of the Lehigh Valley metro area.

Denver's temperature/precipitation/snowfall measurements were taken at Stapleton International Airport (1981-1995) and Denver International Airport (1995-2010). While Stapleton is quite a bit closer to the city than the new Denver International Airport (19 miles closer!), both sets of measurements were taken relatively far from the actual urban area, which is generally a few degrees warmer than the surrounding areas, and gets a different amount of precipitation. NOAA does have data from Denver Water (near downtown), but it starts in 1997 as opposed to 1981, which is when both Denver's and Allentown's airport data begin. For a consistent comparison, I chose to use the Denver Airport data.

For your enjoyment, here is a map of Denver's new and old airports:

View Denver Airport Locations in a larger map

Data Sources

• Temperature/Precipitation/Snowfall: NOAA
• Denver
• Allentown
• Average Relative Humidity: NOAA
• US Cities
• Mean Daily Sunshine Hours: Hong Kong Observatory
• Denver
• Philadelphia (closest available measurement to Allentown)