Apple River
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Apple River clear sky chart from 2005-11-06 to 2025-08-05.

This page is a summary of past forecasts. Even though it's based only on forecasts, some people use these pages as clue to a site's climate. But climate data based on actual observation should be preferred (if you can find it!).

Cloud, Transparency and Seeing forecasts are summarized individually. But because good observing conditions require a combination of minimum cloud cover, transparency and seeing, the individual forecast summaries can be difficult to interpret. The observing conditions section counts the combinations of conditions needed for common types of astronomical observation.

Observing Conditions

The following tables count the occurrence of the combinations of forecast and darkness conditions needed for different observations. Conditions are rated by by what percentage of the hours the observation would likely be attempted are usable.

Observation Type	Minimum conditions for hour to be usable				Out of hours
	Clear of Clouds	Transparency	Seeing	Sky Brightness
Planetary:	50%	(no limit)	Average	(no limit)	Nighttime Hours
Deep Sky:	70%	Average	(no limit)	5.9	Nighttime Hours
CCD Imaging:	70%	Below Average	Poor	(no limit)	Nighttime Hours

Percentages are of nighttime hours per month, or per year, when a particular observing conditions was met. Deep Sky percentages never exceed 50% because the moon is up half the time. Deep sky percentages are much lower for charts at high latitudes because of fewer dark hours in the summer.

Overall

By Month

Individual Forecasts

The length of each colored bar in the "occurrence of each Forecast" column is proportional to the number of times the chart forecast that color. The percentages are of the total number of hours per month, or per year, with a particular forecast. The colors as the same as those used in clear sky charts.

Note: Transparency probabilities are only counted for those hours that have 30% or less cloud cover. Seeing probabilities are only counted for those hours that have 80% or less cloud cover. If that's too tricky, try Observing Conditions instead.

Overall

		Occurrence of each Forecast	Data Points
Cloud Cover	Day	12% 9% 3 8% 5% 4 5% 4 6% 7% 38%	126141
	Night	12% 10% 4 8% 5% 4 4 3 5% 6% 39%	122203
Transparency	Day	44% 5% 12% 24% 13% 1	129637
	Night	45% 5% 11% 23% 14% 2	126780
Seeing	Day	17% 14% 31% 23% 11% 3	16927
	Night	17% 11% 32% 28% 10% 1	26746

By Month

Percentage Cloud Cover SE (2006-)
Color Meanings: Overcast 90% covered 80% covered 70% covered 60% covered 50% covered 40% covered 30% covered 20% covered 10% covered Clear
Month	Days in Month		Occurrence of each Forecast	Data Points
January	1st to 10th	Day	8% 10% 7% 17% 8% 7% 5% 3 4 4 26%	3617
	11th to 20th	Day	7% 8% 7% 12% 6% 4 5% 6% 9% 7% 28%	3620
	21st to end	Day	11% 15% 7% 10% 4 3 3 2 5% 7% 34%	4327
February	1st to 10th	Day	12% 12% 5% 10% 6% 5% 5% 4 5% 6% 29%	1800
	11th to 20th	Day	13% 10% 4 8% 5% 5% 6% 3 5% 6% 36%	1855
	21st to end	Day	13% 12% 4 10% 6% 4 4 3 4 6% 35%	1650
March	1st to 10th	Day	16% 8% 3 6% 4 3 3 2 4 6% 46%	4480
	11th to 20th	Day	11% 6% 3 7% 5% 4 4 3 5% 9% 44%	4928
	21st to end	Day	20% 13% 4 10% 6% 4 4 3 5% 5% 27%	5822
April	1st to 10th	Day	17% 13% 3 7% 5% 4 4 4 5% 6% 31%	2400
	11th to 20th	Day	17% 10% 3 8% 5% 4 4 4 5% 6% 33%	2374
	21st to end	Day	19% 9% 3 7% 4 5% 4 3 5% 7% 33%	2410
May	1st to 10th	Day	15% 8% 3 7% 5% 4 5% 3 6% 7% 38%	6133
	11th to 20th	Day	13% 6% 2 7% 4 4 5% 4 5% 7% 42%	6319
	21st to end	Day	13% 7% 2 7% 5% 5% 5% 4 6% 8% 37%	6935
June	1st to 10th	Day	10% 5% 2 7% 4 5% 5% 5% 6% 8% 44%	2800
	11th to 20th	Day	11% 6% 2 6% 4 4 5% 4 7% 9% 42%	2800
	21st to end	Day	11% 7% 2 6% 5% 5% 5% 4 6% 8% 39%	2800
July	1st to 10th	Day	9% 6% 3 7% 5% 6% 6% 5% 7% 10% 37%	6360
	11th to 20th	Day	9% 6% 2 6% 5% 4 4 4 6% 9% 46%	6360
	21st to end	Day	10% 6% 3 8% 5% 6% 6% 4 7% 9% 37%	6924
August	1st to 10th	Day	8% 6% 2 7% 5% 4 6% 5% 7% 9% 40%	4292
	11th to 20th	Day	11% 5% 2 6% 4 4 5% 4 6% 8% 46%	3855
	21st to end	Day	8% 6% 2 6% 4 4 4 4 6% 8% 47%	4180
September	1st to 10th	Day	12% 5% 2 7% 4 4 5% 3 4 8% 46%	2280
	11th to 20th	Day	12% 5% 1 5% 3 2 4 3 5% 8% 53%	2247
	21st to end	Day	12% 8% 2 5% 4 4 4 3 5% 8% 44%	2085
October	1st to 10th	Day	12% 7% 3 5% 4 3 3 3 4 6% 48%	1900
	11th to 20th	Day	17% 9% 3 8% 4 4 4 3 5% 5% 39%	1900
	21st to end	Day	18% 9% 2 7% 4 4 3 3 5% 6% 40%	1961
November	1st to 10th	Day	12% 8% 3 7% 5% 4 3 3 4 6% 44%	1762
	11th to 20th	Day	13% 13% 3 9% 5% 5% 4 3 6% 6% 34%	1765
	21st to end	Day	13% 13% 4 9% 5% 4 3 3 4 6% 36%	1600
December	1st to 10th	Day	8% 9% 4 8% 5% 4 4 4 5% 8% 41%	2610
	11th to 20th	Day	14% 13% 5% 13% 7% 5% 5% 4 5% 6% 22%	3008
	21st to end	Day	18% 23% 9% 13% 5% 4 3 3 4 4 13%	3982
January	1st to 10th	Night	9% 11% 6% 16% 6% 5% 4 3 4 5% 31%	6348
	11th to 20th	Night	10% 13% 6% 13% 7% 6% 5% 5% 8% 5% 22%	6360
	21st to end	Night	12% 14% 7% 10% 5% 5% 4 3 4 5% 31%	6646
February	1st to 10th	Night	12% 13% 4 10% 6% 5% 4 4 4 5% 32%	2600
	11th to 20th	Night	10% 11% 4 9% 6% 4 4 3 5% 5% 39%	2430
	21st to end	Night	15% 12% 4 8% 4 4 3 3 4 5% 38%	1980
March	1st to 10th	Night	17% 10% 4 6% 4 3 4 3 3 4 42%	5373
	11th to 20th	Night	9% 7% 2 5% 4 4 4 3 5% 8% 49%	5076
	21st to end	Night	20% 12% 6% 11% 5% 5% 4 3 4 5% 26%	5106
April	1st to 10th	Night	16% 10% 3 6% 4 4 4 3 4 6% 40%	2000
	11th to 20th	Night	17% 8% 3 7% 5% 4 4 2 4 6% 39%	1975
	21st to end	Night	16% 9% 3 7% 5% 5% 5% 3 6% 7% 36%	1990
May	1st to 10th	Night	16% 9% 2 7% 4 4 4 3 5% 6% 39%	3771
	11th to 20th	Night	11% 6% 2 5% 5% 4 5% 4 5% 7% 45%	3596
	21st to end	Night	14% 7% 2 6% 4 4 4 4 6% 8% 42%	3942
June	1st to 10th	Night	8% 4 2 7% 4 4 5% 4 7% 7% 47%	1600
	11th to 20th	Night	12% 5% 2 4 4 4 4 5% 6% 9% 45%	1600
	21st to end	Night	11% 6% 2 6% 4 4 5% 3 6% 7% 46%	1600
July	1st to 10th	Night	12% 8% 2 7% 4 4 4 4 7% 9% 40%	3618
	11th to 20th	Night	6% 4 2 5% 4 4 4 3 6% 9% 52%	3617
	21st to end	Night	8% 5% 2 6% 5% 4 4 4 7% 8% 47%	3947
August	1st to 10th	Night	7% 4 2 5% 4 4 4 4 6% 8% 52%	2733
	11th to 20th	Night	8% 6% 2 5% 4 4 4 3 5% 7% 52%	2978
	21st to end	Night	9% 5% 2 5% 4 4 4 3 5% 8% 50%	3476
September	1st to 10th	Night	9% 4 2 5% 3 4 4 3 4 7% 56%	1900
	11th to 20th	Night	10% 4 1 6% 3 4 4 4 5% 6% 52%	1912
	21st to end	Night	10% 6% 1 5% 3 3 5% 4 5% 7% 51%	2092
October	1st to 10th	Night	11% 5% 2 5% 3 4 4 3 5% 6% 52%	2280
	11th to 20th	Night	15% 8% 3 5% 4 4 3 2 5% 6% 45%	2280
	21st to end	Night	17% 8% 3 6% 5% 5% 4 3 5% 6% 38%	2636
November	1st to 10th	Night	12% 8% 3 7% 4 3 3 3 5% 6% 48%	2536
	11th to 20th	Night	13% 12% 4 9% 5% 4 5% 3 5% 5% 36%	2630
	21st to end	Night	16% 11% 4 8% 5% 3 3 3 4 7% 36%	2800
December	1st to 10th	Night	8% 8% 3 7% 6% 6% 5% 4 6% 7% 42%	4580
	11th to 20th	Night	14% 15% 5% 11% 5% 4 4 4 4 6% 28%	5199
	21st to end	Night	19% 21% 7% 12% 5% 4 4 3 4 5% 16%	6996

Transparency (when cloud cover <= 30%)
Color Meanings: Too cloudy to forecast Poor Below Average Average Above average Transparent
Month	Days in Month		Occurrence of each Forecast	Data Points
January	1st to 10th	Day	62% 4 9% 17% 7%	3618
	11th to 20th	Day	51% 6% 13% 10% 18% 2	3620
	21st to end	Day	53% 4 15% 18% 10%	4327
February	1st to 10th	Day	55% 5% 13% 17% 10% 1	1800
	11th to 20th	Day	49% 5% 12% 23% 10% 2	1864
	21st to end	Day	50% 7% 10% 21% 10% 2	1650
March	1st to 10th	Day	41% 5% 11% 29% 11% 4	4480
	11th to 20th	Day	38% 5% 12% 32% 12% 1	4928
	21st to end	Day	59% 6% 11% 14% 8% 1	5824
April	1st to 10th	Day	53% 6% 10% 21% 10%	2400
	11th to 20th	Day	50% 7% 10% 21% 11% 2	2374
	21st to end	Day	50% 6% 11% 19% 12% 1	2410
May	1st to 10th	Day	44% 6% 9% 21% 19%	6168
	11th to 20th	Day	42% 6% 9% 28% 14% 1	6323
	21st to end	Day	43% 6% 11% 27% 11% 2	6949
June	1st to 10th	Day	37% 9% 12% 25% 16% 1	2800
	11th to 20th	Day	37% 7% 13% 23% 18% 2	2800
	21st to end	Day	41% 8% 14% 24% 12% 2	2800
July	1st to 10th	Day	42% 5% 14% 28% 10% 1	6291
	11th to 20th	Day	36% 5% 14% 30% 14% 1	6285
	21st to end	Day	43% 5% 15% 20% 15% 1	6728
August	1st to 10th	Day	38% 7% 15% 27% 13% 1	4277
	11th to 20th	Day	36% 5% 13% 30% 15% 1	3894
	21st to end	Day	34% 5% 14% 31% 15% 2	4179
September	1st to 10th	Day	37% 8% 10% 25% 18% 2	2280
	11th to 20th	Day	31% 6% 12% 32% 17% 2	2247
	21st to end	Day	38% 6% 10% 27% 18% 1	2085
October	1st to 10th	Day	24% 4 6% 37% 28% 1	3160
	11th to 20th	Day	34% 3 10% 25% 25% 3	3140
	21st to end	Day	42% 4 9% 29% 14% 3	3212
November	1st to 10th	Day	41% 6% 14% 24% 13% 2	1762
	11th to 20th	Day	51% 5% 14% 19% 9% 1	1765
	21st to end	Day	50% 6% 16% 21% 7% 1	1600
December	1st to 10th	Day	43% 4 18% 29% 6% 1	2610
	11th to 20th	Day	62% 5% 12% 13% 7% 1	3005
	21st to end	Day	75% 5% 8% 8% 4	3982
January	1st to 10th	Night	56% 5% 10% 20% 9% 1	6348
	11th to 20th	Night	61% 5% 10% 10% 14% 1	6360
	21st to end	Night	56% 3 12% 18% 11%	6646
February	1st to 10th	Night	53% 5% 13% 16% 12% 2	2600
	11th to 20th	Night	47% 6% 10% 22% 13% 1	2431
	21st to end	Night	49% 4 13% 20% 11% 3	1980
March	1st to 10th	Night	47% 4 10% 21% 13% 5%	5373
	11th to 20th	Night	34% 5% 10% 34% 13% 3	5076
	21st to end	Night	62% 4 9% 16% 8% 1	5106
April	1st to 10th	Night	45% 6% 11% 23% 13% 2	2000
	11th to 20th	Night	47% 5% 8% 20% 17% 3	1975
	21st to end	Night	46% 6% 13% 21% 12% 2	1990
May	1st to 10th	Night	44% 6% 11% 17% 19% 2	3798
	11th to 20th	Night	36% 8% 13% 23% 17% 3	3597
	21st to end	Night	38% 7% 11% 28% 15% 2	3950
June	1st to 10th	Night	32% 9% 13% 26% 19% 2	1600
	11th to 20th	Night	34% 7% 12% 24% 20% 3	1600
	21st to end	Night	37% 8% 13% 23% 16% 4	1600
July	1st to 10th	Night	41% 4 14% 26% 13% 2	3580
	11th to 20th	Night	30% 4 15% 31% 19% 1	3572
	21st to end	Night	36% 5% 18% 22% 17% 3	3832
August	1st to 10th	Night	30% 5% 15% 31% 18% 1	2724
	11th to 20th	Night	33% 3 13% 33% 17% 1	3005
	21st to end	Night	32% 5% 12% 29% 17% 4	3476
September	1st to 10th	Night	29% 6% 12% 27% 25% 2	1900
	11th to 20th	Night	31% 6% 12% 31% 18% 3	1912
	21st to end	Night	32% 7% 10% 30% 19% 2	2092
October	1st to 10th	Night	25% 3 6% 35% 29% 2	3800
	11th to 20th	Night	33% 3 9% 23% 29% 3	3779
	21st to end	Night	45% 4 9% 26% 15% 2	4335
November	1st to 10th	Night	38% 5% 12% 26% 17% 2	2536
	11th to 20th	Night	50% 6% 12% 19% 12% 1	2630
	21st to end	Night	49% 5% 13% 23% 10% 1	2800
December	1st to 10th	Night	42% 4 16% 29% 8% 1	4580
	11th to 20th	Night	58% 4 13% 17% 7%	5201
	21st to end	Night	72% 5% 7% 11% 4	6996

Seeing (when cloud cover <= 80%)
Color Meanings: Too cloudy to forecast Bad 1/5 Poor 2/5 Average 3/5 Good 4/5 Excellent 5/5
Month	Days in Month		Occurrence of each Forecast	Data Points
January	1st to 10th	Day	19% 16% 33% 25% 6% 1	300
	11th to 20th	Day	20% 20% 42% 14% 3 1	300
	21st to end	Day	21% 24% 36% 16% 3 1	330
February	1st to 10th	Day	19% 25% 36% 16% 3	300
	11th to 20th	Day	23% 28% 30% 16% 3	300
	21st to end	Day	24% 24% 42% 10% 1	249
March	1st to 10th	Day	20% 25% 42% 10% 3	300
	11th to 20th	Day	25% 21% 37% 12% 4 1	300
	21st to end	Day	30% 19% 30% 16% 4 1	483
April	1st to 10th	Day	29% 19% 32% 15% 4	500
	11th to 20th	Day	28% 20% 25% 19% 7% 1	492
	21st to end	Day	24% 17% 31% 19% 7% 1	500
May	1st to 10th	Day	20% 16% 33% 23% 7% 2	618
	11th to 20th	Day	22% 15% 30% 21% 10% 2	725
	21st to end	Day	17% 13% 30% 24% 12% 4	789
June	1st to 10th	Day	10% 11% 31% 29% 14% 4	730
	11th to 20th	Day	13% 9% 35% 27% 11% 3	730
	21st to end	Day	15% 12% 30% 28% 11% 4	730
July	1st to 10th	Day	10% 4 24% 30% 21% 10%	721
	11th to 20th	Day	10% 7% 30% 30% 18% 6%	718
	21st to end	Day	10% 4 28% 33% 18% 6%	794
August	1st to 10th	Day	7% 4 23% 36% 23% 7%	697
	11th to 20th	Day	13% 7% 24% 25% 23% 9%	557
	21st to end	Day	10% 6% 22% 33% 21% 7%	539
September	1st to 10th	Day	14% 9% 26% 28% 18% 5%	490
	11th to 20th	Day	11% 4 24% 32% 22% 7%	490
	21st to end	Day	16% 16% 26% 24% 16% 3	485
October	1st to 10th	Day	16% 16% 29% 26% 12% 1	300
	11th to 20th	Day	22% 25% 30% 17% 7%	300
	21st to end	Day	30% 17% 31% 17% 4 1	330
November	1st to 10th	Day	20% 17% 39% 16% 6% 2	300
	11th to 20th	Day	20% 23% 35% 15% 6%	300
	21st to end	Day	26% 15% 40% 15% 3	300
December	1st to 10th	Day	16% 24% 39% 15% 5% 1	300
	11th to 20th	Day	18% 18% 38% 20% 5%	300
	21st to end	Day	25% 22% 36% 15% 2	330
January	1st to 10th	Night	15% 17% 38% 23% 6% 1	1000
	11th to 20th	Night	18% 17% 38% 22% 4 1	1000
	21st to end	Night	21% 13% 38% 24% 4	1100
February	1st to 10th	Night	20% 16% 37% 22% 5%	1000
	11th to 20th	Night	16% 18% 38% 24% 3	876
	21st to end	Night	23% 16% 39% 19% 2	660
March	1st to 10th	Night	24% 15% 36% 20% 5%	800
	11th to 20th	Night	19% 12% 36% 27% 6%	644
	21st to end	Night	24% 13% 36% 22% 4	660
April	1st to 10th	Night	20% 18% 34% 23% 4	600
	11th to 20th	Night	21% 16% 31% 26% 6%	593
	21st to end	Night	21% 12% 31% 29% 7% 1	600
May	1st to 10th	Night	17% 11% 38% 28% 6% 1	600
	11th to 20th	Night	19% 8% 33% 30% 10%	591
	21st to end	Night	14% 4 33% 34% 13% 1	650
June	1st to 10th	Night	9% 4 31% 45% 11%	600
	11th to 20th	Night	13% 5% 34% 37% 12%	600
	21st to end	Night	13% 5% 28% 40% 15% 1	600
July	1st to 10th	Night	8% 3 18% 39% 28% 4	585
	11th to 20th	Night	8% 3 24% 38% 24% 3	582
	21st to end	Night	7% 2 21% 44% 25% 1	657
August	1st to 10th	Night	6% 3 16% 45% 27% 2	579
	11th to 20th	Night	10% 1 16% 39% 29% 5%	564
	21st to end	Night	10% 3 19% 43% 22% 3	627
September	1st to 10th	Night	10% 5% 22% 38% 20% 5%	570
	11th to 20th	Night	11% 4 24% 33% 24% 4	582
	21st to end	Night	13% 10% 27% 33% 17% 1	760
October	1st to 10th	Night	14% 8% 28% 33% 16% 1	760
	11th to 20th	Night	19% 13% 32% 27% 9%	760
	21st to end	Night	22% 15% 32% 24% 6%	836
November	1st to 10th	Night	17% 13% 38% 23% 9% 1	780
	11th to 20th	Night	19% 18% 36% 21% 5%	830
	21st to end	Night	21% 16% 36% 20% 7%	1000
December	1st to 10th	Night	19% 16% 38% 22% 5%	1000
	11th to 20th	Night	22% 15% 34% 24% 5%	1000
	21st to end	Night	28% 15% 35% 20% 3	1100

Page generated at 2025-08-02 00:32:27. Version ac07

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