First off, I used the Julian calendar because it makes this sort of study easier. The Julian calendar assigns consecutive dates for each day starting with day 1 (January 1st) and ending with day 365 (December 31st most years). So, in analyzing a series of numbers like ice-out dates, there are three characteristics engineering types look for:

Mode: the most common number in the list, in this case the date on which ice-out has occurred most often. For Rangeley we, have a tie between May 4th and May 11th

Mean: also known as the average. May 7th it is!

Median: arranging the list in rank order (for ice out earliest to latest), the number/date in the middle of the list is the median. This characteristic is not particularly informative for ice out data and it pretty much matches the average.

Attached is my study, the utility of which is constrained by several factors:
Input error by me (garbage in = garbage out!)
The arbitrary and capricious nature of the official ice-out declaration. It is not only subjective, it is hard to observe the condition of the ice during the hours between sunset and sunrise!
This is a pathetically poor sample both in size and data distribution (we only have the last 140 consecutive years). Rangeley Lake has existed, more or less in its current state, for well over 12,000 years. We have no data for years 1 thru 11,860!! Imagine you watched only the last play of the last 140 football games. What would that tell you? The answer is: Nothing
For the purpose of ice-out, our calendar has a huge error built in: It takes the Earth 365 days plus 6 hours to orbit the Sun. So unless you record the time of ice-out and then add the requisite correction factor, (which, in 25% of the years, is 18 hours!) what you have is a date plus or minus one day.
But if your objective  is to win the Highlander ice-out contest, this data is gold. Please remember me when you win.

Caution: Connecting the ice-out date with ambient temperature conditions ignores many other factors that influence ice-out. Wind and late season snow events being two of the biggies. I think it was last year that ice-out was unexpected early (May 11) and was caused by a big wind. The moving, unmelted, ice sheet did a lot of damage to shorelines and docks.

Rangeley Ice Out Dates
Earliest to Latest
1880 134 104 April 14th or was it really April 15th?
136 104
144 106
136 106
134 109
136 111
124 112
137 113
142 113
120 114
129 114
134 115
130 115
137 116
122 116
127 116
131 117
133 117
125 118
128 ave 132 May 12th 119
119
1900 136 119
124 119
118 119
117 120
135 120
125 120
133 120
139 121
131 121
132 121
109 121
131 122
130 122
124 122
141 122
119 122
129 122
137 123
123 123
123 123
ave 128 May 8th 123
1920 140 124
104 124
124 124
129 124
131 124
119 124
138 124
119 125 Mode 1 May 5th 10 times
134 125
130 125
126 125
116 125
127 125
127 125
125 125
131 125
125 125 Mode 1
131 126
119 126
134 126
ave 126 May 6th 126
1940 140 126
116 126
125 126 Median 6-May
140 127 Median 7-May
132 127
14-Apr 104 127
122 127
133 127
122 127
114 127
128 127
122 128
123 128
114 128
126 128
120 128
136 129
121 129
127 129
128 129
ave 125 May 5th 129
1960 125 130
135 130
137 130
127 130
127 130
129 130
137 131 Mode 2 May 11th 10 times
130 131
116 131
132 131
135 131
135 131
1972 144 131
124 131
135 131
132 131 Mode 2
119 132
127 132
137 132
121 ave 130 May 10th 132
133
1980 126 133
120 133
133 133
126 133
125 133
130 134
117 134
111 134
126 134
131 134
125 135
121 135
133 135
122 135
128 135
125 136
130 136
133 136
113 136
123 136
ave 125 137
2000 121 137
126 137
115 137
126 137
124 137
127 138
113 139
131 140
125 140
115 140
106 141
124 142
106 144
122 144 May 24th or was it really May 23rd?
131
128
112
120
129
131
ave 122
140 yr ave 127 May 7th

Contribution by Bill Pierce is the following graph:


Only subscribers are eligible to post comments. Please subscribe or to participate in the conversation. Here’s why.

Use the form below to reset your password. When you've submitted your account email, we will send an email with a reset code.