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 2024-04-03.

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	13% 9% 4 7% 6% 3 5% 5% 5% 7% 36%	78788
	Night	13% 9% 4 7% 5% 3 4 4 5% 7% 38%	81392
Transparency	Day	46% 7% 13% 21% 11% 1	78488
	Night	46% 6% 12% 21% 13% 2	81212
Seeing	Day	17% 14% 31% 24% 11% 4	14951
	Night	17% 11% 32% 28% 10% 1	25017

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	11% 13% 9% 13% 8% 4 4 4 4 4 27%	2527
	11th to 20th	Day	11% 10% 5% 13% 9% 3 6% 8% 9% 7% 20%	2530
	21st to end	Day	15% 19% 9% 11% 5% 3 4 3 4 5% 21%	3016
February	1st to 10th	Day	12% 12% 6% 9% 7% 3 5% 6% 5% 6% 30%	1710
	11th to 20th	Day	13% 9% 4 7% 5% 4 6% 4 5% 6% 36%	1759
	21st to end	Day	14% 12% 5% 9% 6% 3 4 4 3 6% 34%	1570
March	1st to 10th	Day	14% 10% 5% 7% 5% 3 5% 4 5% 6% 36%	1900
	11th to 20th	Day	13% 9% 4 7% 6% 3 4 4 5% 8% 39%	2065
	21st to end	Day	19% 12% 4 7% 7% 3 4 4 5% 6% 28%	2444
April	1st to 10th	Day	18% 11% 5% 7% 6% 3 4 4 5% 7% 31%	2184
	11th to 20th	Day	17% 9% 4 7% 6% 3 4 5% 5% 6% 34%	2134
	21st to end	Day	20% 8% 4 6% 5% 4 3 5% 5% 7% 33%	2168
May	1st to 10th	Day	16% 9% 4 7% 7% 3 5% 6% 6% 8% 29%	2443
	11th to 20th	Day	17% 8% 3 6% 5% 4 6% 5% 5% 6% 33%	2479
	21st to end	Day	14% 6% 3 7% 7% 4 6% 5% 6% 7% 36%	2725
June	1st to 10th	Day	10% 5% 2 6% 5% 3 5% 6% 6% 8% 44%	2520
	11th to 20th	Day	11% 6% 3 5% 4 3 5% 6% 6% 8% 43%	2520
	21st to end	Day	11% 6% 3 6% 6% 4 6% 6% 5% 9% 39%	2520
July	1st to 10th	Day	7% 4 2 4 5% 3 5% 5% 6% 10% 47%	2520
	11th to 20th	Day	8% 4 2 5% 5% 3 5% 6% 6% 11% 46%	2520
	21st to end	Day	6% 4 3 5% 6% 4 6% 5% 7% 9% 45%	2743
August	1st to 10th	Day	6% 6% 2 6% 6% 3 6% 7% 8% 11% 40%	2403
	11th to 20th	Day	11% 5% 2 5% 5% 3 5% 6% 6% 8% 45%	2199
	21st to end	Day	10% 5% 3 5% 5% 3 5% 5% 6% 8% 47%	2376
September	1st to 10th	Day	12% 5% 2 6% 5% 3 5% 4 4 8% 45%	2160
	11th to 20th	Day	13% 5% 1 4 4 1 4 4 4 7% 54%	2129
	21st to end	Day	12% 8% 3 5% 4 3 4 4 5% 9% 44%	1976
October	1st to 10th	Day	13% 8% 3 5% 5% 3 4 4 4 7% 46%	1800
	11th to 20th	Day	18% 9% 4 7% 5% 3 4 4 5% 5% 37%	1800
	21st to end	Day	19% 8% 3 5% 4 3 4 4 5% 5% 40%	1858
November	1st to 10th	Day	12% 7% 3 6% 6% 3 4 4 4 6% 44%	1672
	11th to 20th	Day	13% 12% 4 8% 6% 3 5% 4 5% 7% 34%	1677
	21st to end	Day	13% 11% 5% 7% 6% 3 4 3 4 6% 38%	1520
December	1st to 10th	Day	14% 12% 4 8% 6% 3 5% 4 4 6% 33%	1520
	11th to 20th	Day	14% 12% 5% 9% 7% 4 5% 5% 5% 7% 29%	1918
	21st to end	Day	20% 20% 9% 11% 6% 3 4 4 4 4 15%	2783
January	1st to 10th	Night	12% 12% 8% 11% 7% 3 4 4 4 5% 29%	4428
	11th to 20th	Night	12% 15% 7% 12% 8% 3 4 6% 8% 5% 20%	4440
	21st to end	Night	16% 17% 8% 10% 7% 4 4 3 4 5% 22%	4646
February	1st to 10th	Night	12% 11% 5% 9% 7% 4 5% 5% 4 6% 32%	2470
	11th to 20th	Night	10% 9% 4 8% 7% 3 5% 4 5% 5% 40%	2306
	21st to end	Night	16% 11% 4 7% 6% 3 4 4 4 5% 37%	1884
March	1st to 10th	Night	16% 11% 4 6% 6% 2 5% 4 4 6% 36%	2280
	11th to 20th	Night	12% 8% 4 5% 5% 4 5% 4 4 9% 41%	2132
	21st to end	Night	19% 11% 5% 8% 5% 4 5% 4 4 6% 29%	2153
April	1st to 10th	Night	16% 9% 4 6% 5% 3 4 4 4 6% 39%	1820
	11th to 20th	Night	18% 8% 4 7% 5% 3 4 3 4 6% 38%	1775
	21st to end	Night	16% 9% 3 6% 5% 4 5% 4 5% 8% 35%	1792
May	1st to 10th	Night	15% 7% 2 7% 5% 4 6% 5% 6% 9% 35%	1514
	11th to 20th	Night	18% 8% 3 5% 5% 3 5% 5% 5% 6% 37%	1416
	21st to end	Night	12% 5% 3 6% 3 3 5% 4 7% 11% 42%	1551
June	1st to 10th	Night	8% 4 3 6% 5% 3 5% 5% 6% 8% 47%	1440
	11th to 20th	Night	12% 5% 2 3 5% 3 4 5% 6% 9% 47%	1440
	21st to end	Night	11% 5% 2 5% 4 3 5% 5% 6% 8% 46%	1440
July	1st to 10th	Night	7% 4 2 3 3 2 3 4 6% 12% 55%	1440
	11th to 20th	Night	6% 3 2 3 4 2 4 4 5% 11% 56%	1440
	21st to end	Night	7% 4 1 4 4 3 4 5% 7% 9% 52%	1575
August	1st to 10th	Night	5% 3 2 5% 5% 3 5% 4 6% 9% 52%	1532
	11th to 20th	Night	7% 5% 2 4 4 4 3 4 5% 7% 55%	1702
	21st to end	Night	8% 5% 2 4 4 3 4 4 5% 7% 54%	1980
September	1st to 10th	Night	10% 4 2 5% 4 3 4 5% 4 7% 54%	1800
	11th to 20th	Night	11% 4 1 4 4 3 4 5% 5% 7% 52%	1811
	21st to end	Night	10% 5% 2 4 4 2 4 5% 5% 6% 51%	1981
October	1st to 10th	Night	12% 5% 2 4 4 3 4 4 4 6% 51%	2160
	11th to 20th	Night	16% 7% 3 5% 4 3 3 3 5% 7% 43%	2160
	21st to end	Night	18% 8% 3 5% 6% 3 4 4 4 6% 38%	2497
November	1st to 10th	Night	11% 7% 3 6% 5% 2 3 3 4 6% 50%	2406
	11th to 20th	Night	12% 11% 4 8% 6% 3 5% 4 4 5% 37%	2498
	21st to end	Night	16% 9% 4 7% 6% 2 4 3 4 7% 38%	2660
December	1st to 10th	Night	13% 11% 4 10% 6% 4 5% 5% 5% 6% 31%	2660
	11th to 20th	Night	13% 13% 5% 9% 6% 3 4 5% 4 7% 30%	3279
	21st to end	Night	20% 16% 7% 11% 6% 3 5% 4 4 5% 19%	4884

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	61% 5% 12% 15% 6%	2528
	11th to 20th	Day	58% 8% 15% 11% 7% 1	2530
	21st to end	Day	66% 5% 11% 13% 5%	3016
February	1st to 10th	Day	54% 5% 13% 18% 10% 1	1710
	11th to 20th	Day	48% 5% 12% 23% 10% 2	1768
	21st to end	Day	51% 7% 10% 20% 9% 2	1570
March	1st to 10th	Day	49% 7% 14% 20% 9% 1	1900
	11th to 20th	Day	44% 6% 13% 25% 11% 1	2065
	21st to end	Day	57% 7% 11% 18% 7% 1	2444
April	1st to 10th	Day	53% 7% 10% 21% 9%	2184
	11th to 20th	Day	50% 7% 9% 21% 11% 2	2134
	21st to end	Day	51% 6% 11% 19% 11% 2	2168
May	1st to 10th	Day	51% 8% 14% 19% 7%	2443
	11th to 20th	Day	50% 7% 11% 21% 11%	2483
	21st to end	Day	47% 8% 12% 18% 14% 2	2725
June	1st to 10th	Day	37% 9% 13% 25% 15% 1	2520
	11th to 20th	Day	37% 7% 13% 23% 19% 2	2520
	21st to end	Day	41% 9% 14% 23% 12% 1	2520
July	1st to 10th	Day	33% 9% 15% 26% 14% 2	2451
	11th to 20th	Day	32% 10% 16% 26% 14% 2	2445
	21st to end	Day	33% 9% 16% 25% 14% 3	2591
August	1st to 10th	Day	34% 11% 16% 28% 11% 1	2388
	11th to 20th	Day	36% 8% 14% 25% 16% 1	2199
	21st to end	Day	33% 8% 12% 26% 17% 3	2376
September	1st to 10th	Day	38% 8% 10% 25% 17% 2	2160
	11th to 20th	Day	31% 6% 12% 33% 16% 2	2129
	21st to end	Day	38% 6% 11% 28% 17% 1	1976
October	1st to 10th	Day	39% 7% 11% 28% 16% 1	1800
	11th to 20th	Day	49% 4 12% 21% 13% 1	1800
	21st to end	Day	46% 6% 12% 23% 12% 1	1858
November	1st to 10th	Day	40% 6% 14% 24% 13% 2	1672
	11th to 20th	Day	50% 6% 14% 19% 9% 1	1677
	21st to end	Day	49% 6% 17% 21% 7% 1	1520
December	1st to 10th	Day	53% 7% 13% 17% 8% 2	1520
	11th to 20th	Day	54% 7% 16% 14% 8% 1	1915
	21st to end	Day	72% 7% 9% 8% 4	2783
January	1st to 10th	Night	56% 7% 11% 17% 8%	4428
	11th to 20th	Night	62% 6% 11% 13% 8%	4440
	21st to end	Night	67% 4 9% 14% 5% 1	4646
February	1st to 10th	Night	52% 5% 13% 17% 12% 1	2470
	11th to 20th	Night	46% 7% 11% 22% 14% 1	2307
	21st to end	Night	50% 5% 12% 20% 10% 3	1884
March	1st to 10th	Night	50% 6% 13% 20% 11% 1	2280
	11th to 20th	Night	41% 6% 12% 23% 15% 2	2132
	21st to end	Night	57% 5% 9% 18% 8% 2	2153
April	1st to 10th	Night	47% 6% 11% 21% 13% 2	1820
	11th to 20th	Night	48% 6% 7% 19% 17% 3	1775
	21st to end	Night	47% 6% 13% 20% 12% 2	1792
May	1st to 10th	Night	45% 8% 15% 20% 12%	1514
	11th to 20th	Night	46% 7% 12% 20% 14% 1	1417
	21st to end	Night	35% 9% 16% 22% 17% 1	1552
June	1st to 10th	Night	32% 8% 13% 25% 20% 2	1440
	11th to 20th	Night	32% 8% 11% 24% 21% 3	1440
	21st to end	Night	35% 8% 14% 24% 16% 3	1440
July	1st to 10th	Night	24% 9% 16% 32% 16% 3	1400
	11th to 20th	Night	25% 6% 14% 30% 21% 4	1392
	21st to end	Night	27% 8% 19% 25% 18% 4	1487
August	1st to 10th	Night	28% 7% 16% 32% 15% 2	1523
	11th to 20th	Night	29% 5% 15% 31% 19% 1	1702
	21st to end	Night	28% 7% 12% 29% 19% 5%	1980
September	1st to 10th	Night	30% 7% 12% 26% 24% 2	1800
	11th to 20th	Night	30% 6% 12% 31% 17% 3	1811
	21st to end	Night	32% 7% 11% 30% 19% 2	1981
October	1st to 10th	Night	34% 5% 10% 27% 22% 2	2160
	11th to 20th	Night	41% 5% 12% 23% 18% 1	2160
	21st to end	Night	47% 6% 11% 23% 12% 1	2497
November	1st to 10th	Night	36% 5% 12% 26% 18% 3	2406
	11th to 20th	Night	49% 6% 13% 19% 12% 1	2498
	21st to end	Night	47% 5% 13% 24% 10% 1	2660
December	1st to 10th	Night	54% 6% 12% 20% 8% 1	2660
	11th to 20th	Night	53% 6% 15% 18% 7% 1	3281
	21st to end	Night	68% 6% 8% 12% 4	4884

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	20% 16% 32% 25% 7% 1	270
	11th to 20th	Day	21% 17% 43% 15% 3 1	270
	21st to end	Day	22% 21% 36% 17% 3 1	297
February	1st to 10th	Day	18% 25% 37% 17% 3	270
	11th to 20th	Day	23% 27% 30% 17% 4	270
	21st to end	Day	23% 24% 41% 11% 1	225
March	1st to 10th	Day	18% 24% 44% 11% 3	270
	11th to 20th	Day	24% 22% 36% 12% 4 1	270
	21st to end	Day	30% 18% 29% 17% 4 1	442
April	1st to 10th	Day	29% 18% 33% 16% 5%	428
	11th to 20th	Day	26% 18% 26% 20% 8% 1	412
	21st to end	Day	24% 17% 29% 20% 8% 2	420
May	1st to 10th	Day	21% 15% 32% 24% 6% 2	526
	11th to 20th	Day	22% 15% 31% 21% 9% 2	625
	21st to end	Day	16% 12% 29% 24% 13% 5%	679
June	1st to 10th	Day	8% 10% 32% 30% 15% 5%	630
	11th to 20th	Day	13% 9% 35% 28% 11% 4	630
	21st to end	Day	15% 11% 29% 29% 12% 4	630
July	1st to 10th	Day	9% 5% 22% 32% 21% 11%	621
	11th to 20th	Day	9% 6% 30% 31% 18% 6%	618
	21st to end	Day	9% 5% 29% 34% 18% 6%	684
August	1st to 10th	Day	7% 4 23% 37% 24% 6%	626
	11th to 20th	Day	13% 6% 22% 24% 24% 10%	513
	21st to end	Day	11% 7% 23% 33% 20% 7%	495
September	1st to 10th	Day	15% 10% 25% 28% 17% 5%	450
	11th to 20th	Day	12% 5% 24% 31% 20% 7%	450
	21st to end	Day	16% 16% 25% 24% 17% 3	446
October	1st to 10th	Day	17% 16% 29% 26% 11% 1	270
	11th to 20th	Day	23% 26% 31% 15% 5%	270
	21st to end	Day	31% 18% 30% 16% 5% 1	297
November	1st to 10th	Day	18% 18% 38% 17% 7% 2	270
	11th to 20th	Day	19% 23% 36% 16% 6%	270
	21st to end	Day	25% 14% 42% 16% 4	270
December	1st to 10th	Day	17% 23% 39% 15% 6% 1	270
	11th to 20th	Day	16% 18% 37% 22% 6%	270
	21st to end	Day	24% 24% 37% 14% 1	297
January	1st to 10th	Night	16% 17% 38% 23% 6% 1	950
	11th to 20th	Night	18% 17% 38% 22% 4 1	950
	21st to end	Night	21% 12% 37% 24% 4	1045
February	1st to 10th	Night	20% 15% 37% 23% 5%	950
	11th to 20th	Night	16% 17% 38% 25% 3	832
	21st to end	Night	24% 17% 38% 18% 3	628
March	1st to 10th	Night	24% 15% 36% 20% 5%	760
	11th to 20th	Night	19% 12% 35% 27% 6%	612
	21st to end	Night	24% 13% 36% 22% 4	627
April	1st to 10th	Night	20% 17% 35% 23% 5%	546
	11th to 20th	Night	22% 15% 30% 27% 6%	533
	21st to end	Night	21% 12% 30% 28% 8% 1	540
May	1st to 10th	Night	17% 11% 38% 26% 6% 1	540
	11th to 20th	Night	21% 7% 33% 29% 10%	531
	21st to end	Night	14% 4 34% 33% 15% 1	584
June	1st to 10th	Night	9% 4 30% 45% 12%	540
	11th to 20th	Night	13% 4 32% 38% 12%	540
	21st to end	Night	12% 5% 27% 41% 15% 1	540
July	1st to 10th	Night	7% 3 17% 38% 30% 4	525
	11th to 20th	Night	7% 3 25% 38% 24% 2	522
	21st to end	Night	7% 2 21% 44% 24% 1	591
August	1st to 10th	Night	5% 3 16% 45% 28% 3	537
	11th to 20th	Night	10% 1 15% 38% 30% 5%	534
	21st to end	Night	10% 3 20% 42% 22% 3	594
September	1st to 10th	Night	10% 6% 22% 38% 19% 5%	540
	11th to 20th	Night	11% 4 24% 33% 24% 5%	551
	21st to end	Night	13% 10% 26% 33% 17% 1	720
October	1st to 10th	Night	15% 8% 28% 32% 16% 1	720
	11th to 20th	Night	20% 14% 31% 27% 8%	720
	21st to end	Night	22% 14% 32% 24% 6% 1	792
November	1st to 10th	Night	16% 13% 38% 23% 9% 1	740
	11th to 20th	Night	18% 18% 36% 22% 5%	788
	21st to end	Night	20% 15% 37% 20% 7%	950
December	1st to 10th	Night	20% 15% 38% 22% 5%	950
	11th to 20th	Night	21% 14% 35% 24% 5%	950
	21st to end	Night	27% 16% 35% 20% 2	1045

Page generated at 2024-03-31 05:08:53. Version ac07

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