Sun Statistics

When I got my first weather station for Christmas in 1992, it gave me all the usual weather readings you would expect, such as temperature, wind, humidity, barometric pressure, etc. However, it didn’t give the one statistic everyone wanted to know, which was how much sunshine go we get on any given day.

Moving to Anacortes from Southern California, sunshine was an important part of our lives. The climate change wasn’t as traumatic as I was afraid it was going to be, in fact I quickly grew to enjoy our newfound environment. But everyone still wanted to know how much sunshine we actually got “where it rains all the time”.

Each evening, in addition to recording the daily readings from my weather station, I would also write down the percentage of sunshine I thought we had that day. It wasn’t a perfect solution, but at least I had some data on sunshine. I recorded my first year of sunshine statistics in 1993. To date I have been keeping these records now for thirteen years.

Last year I upgraded my weather station, so now I have a sensor that reads solar radiation. When these readings are charted out on my computer, I can see which days are sunny, and which ones are not, based on how much solar radiation strikes the censor. So, now I have statistical data, besides my subjective data, on which to base my sun statistics.

When reporting my sun statistics, I decided that anything under 25% was a cloudy day. Partial sunny days were between 26% and 74%. Anything 75% or higher I counted as a sunny day.

From the thirteen years of gathering my sun statistics, I’ve found that Anacortes averages 134.7 sunny days a year. We average another 83.8 partial sunny days a year, with 146.6 days counted as overcast. When you add our sunny days and partially sunny days together, I discovered that almost two thirds of our days have more than 25 percent sunshine. The sunniest year I recorded was the first, with 163 sunny days. The year with the least amount of sunny days was 1996, with only 110. When you throw out those two years, the rest of the years are amazingly close to our average of 134.7.

As expected, December turns out to be the darkest month of the year, with only 6.2 sunny days on average. The second darkest month is January with an average of 6.5 sunny days. August wins the prize for the most sunny days with an average of 18, followed close behind by July with an average of 17.6.

Yearly Sun Statistics
Year
Sunny
Partial Sun
Overcast
1993
163
79
123
1994
132
98
135
1995
134
94
137
1996
110
87
169
1997
129
80
156
1998
133
87
145
1999
125
80
160
2000
129
90
147
2001
135
75
154
2002
142
66
157
2003
136
85
144
2004
146
85
138
2005
137
87
141
2006
142
86
142
2007
124
93
148
2008
115
83
168
2009
158
78
129
2010
133
82
150
2011
108
101
156
2012
132
91
143
2013
153
97
115
2014
159
109
97
2015
176
102
87

Monthly Sun Averages
Month
Sunny
Partial Sun
Overcast
Jan
6.5
4.2
20.3
Feb
10
5.5
12.5
March
8.6
8.8
13.4
April
11.4
8.8
9.8
May
12.2
8.8
10
June
12.6
9.2
8.2
July
17.6
7.7
5.7
August
18
7.2
5.8
Sept
15.6
7.3
8.1
Oct
9
8.2
13.8
Nov
7.2
4.9
17.9
Dec
6.2
4
20.8