North Fork Campground
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the North Fork Campground clear sky chart from 2005-11-06 to 2025-05-26.

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	6% 9% 3 7% 4 4 4 3 5% 6% 51%	117717
	Night	6% 10% 3 7% 4 4 4 3 5% 6% 48%	120358
Transparency	Day	32% 6% 9% 19% 20% 15%	117461
	Night	34% 6% 10% 20% 19% 11%	120203
Seeing	Day	9% 9% 25% 29% 20% 8%	15235
	Night	10% 6% 19% 38% 23% 4	24661

By Month

Percentage Cloud Cover SW (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	6% 19% 7% 15% 6% 5% 5% 3 6% 6% 21%	3639
	11th to 20th	Day	6% 13% 5% 13% 6% 5% 4 4 5% 5% 36%	3640
	21st to end	Day	9% 14% 4 8% 4 4 3 3 4 5% 44%	4004
February	1st to 10th	Day	6% 13% 4 9% 5% 5% 4 4 6% 7% 36%	1832
	11th to 20th	Day	7% 15% 6% 11% 6% 5% 4 3 5% 5% 34%	1950
	21st to end	Day	5% 13% 4 11% 6% 4 4 4 5% 7% 36%	1650
March	1st to 10th	Day	5% 17% 5% 10% 6% 5% 5% 4 5% 7% 32%	4518
	11th to 20th	Day	4 11% 4 11% 5% 4 4 4 4 6% 44%	4734
	21st to end	Day	4 13% 5% 11% 6% 5% 5% 4 6% 7% 33%	5837
April	1st to 10th	Day	9% 12% 3 9% 5% 4 4 4 6% 7% 36%	2400
	11th to 20th	Day	6% 12% 3 7% 5% 5% 4 3 5% 7% 44%	2369
	21st to end	Day	7% 9% 3 6% 4 4 4 4 6% 8% 45%	2587
May	1st to 10th	Day	5% 12% 4 7% 4 4 4 4 6% 6% 43%	4240
	11th to 20th	Day	6% 4 1 5% 3 3 3 3 5% 5% 63%	4344
	21st to end	Day	6% 8% 3 5% 4 4 4 3 6% 7% 51%	4886
June	1st to 10th	Day	10% 7% 3 5% 4 4 6% 4 6% 8% 43%	2660
	11th to 20th	Day	6% 5% 2 4 3 4 4 3 5% 8% 57%	2660
	21st to end	Day	3 3 1 3 2 3 3 3 4 6% 69%	2660
July	1st to 10th	Day	1 1 1 2 2 2 2 2 3 4 80%	4420
	11th to 20th	Day	2 2 1 4 3 3 3 3 5% 5% 69%	4420
	21st to end	Day	3 3 1 4 3 3 3 3 5% 5% 67%	4790
August	1st to 10th	Day	4 4 2 4 4 4 3 3 5% 6% 60%	4246
	11th to 20th	Day	2 1 1 2 2 2 2 2 3 4 79%	3908
	21st to end	Day	2 3 1 3 2 2 2 2 4 4 74%	4180
September	1st to 10th	Day	2 3 1 3 2 2 2 3 3 6% 73%	2280
	11th to 20th	Day	5% 5% 1 3 3 4 3 3 3 5% 65%	2132
	21st to end	Day	5% 6% 2 4 2 2 2 2 4 6% 65%	2090
October	1st to 10th	Day	4 5% 2 5% 2 2 3 2 3 4 68%	3490
	11th to 20th	Day	7% 7% 2 4 3 3 3 3 4 6% 58%	3062
	21st to end	Day	4 9% 3 6% 4 4 6% 4 7% 8% 46%	3101
November	1st to 10th	Day	9% 13% 4 8% 5% 3 4 3 5% 6% 40%	1764
	11th to 20th	Day	11% 10% 3 6% 5% 5% 4 4 5% 8% 38%	1800
	21st to end	Day	7% 13% 4 9% 3 3 4 5% 6% 8% 39%	1772
December	1st to 10th	Day	6% 8% 3 6% 4 3 3 3 4 8% 52%	2620
	11th to 20th	Day	12% 13% 3 9% 5% 5% 4 4 7% 7% 30%	3028
	21st to end	Day	13% 15% 5% 10% 6% 4 5% 4 6% 7% 26%	4004
January	1st to 10th	Night	7% 18% 6% 12% 5% 4 4 3 5% 6% 28%	6306
	11th to 20th	Night	8% 16% 5% 10% 4 3 3 2 4 5% 39%	6320
	21st to end	Night	6% 13% 4 8% 4 4 4 3 5% 6% 45%	6952
February	1st to 10th	Night	8% 13% 4 11% 5% 5% 4 4 5% 7% 34%	2565
	11th to 20th	Night	7% 12% 6% 8% 4 5% 4 4 5% 7% 38%	2338
	21st to end	Night	5% 13% 5% 9% 5% 5% 5% 4 6% 7% 36%	1980
March	1st to 10th	Night	6% 17% 4 8% 4 4 4 4 5% 6% 38%	5376
	11th to 20th	Night	7% 12% 4 8% 5% 4 4 3 5% 6% 43%	5264
	21st to end	Night	5% 11% 3 8% 5% 5% 5% 5% 7% 9% 38%	5123
April	1st to 10th	Night	8% 9% 2 8% 5% 5% 4 4 6% 7% 41%	2000
	11th to 20th	Night	6% 10% 3 6% 5% 3 4 4 5% 6% 50%	1979
	21st to end	Night	6% 8% 2 7% 4 4 4 4 6% 7% 48%	1811
May	1st to 10th	Night	7% 9% 3 7% 3 3 4 4 5% 7% 48%	2950
	11th to 20th	Night	4 4 1 4 3 3 4 3 5% 6% 64%	2770
	21st to end	Night	5% 6% 2 5% 3 3 4 3 5% 7% 55%	2805
June	1st to 10th	Night	8% 7% 3 6% 5% 4 5% 4 5% 6% 47%	1520
	11th to 20th	Night	5% 5% 2 4 3 4 3 2 4 5% 62%	1520
	21st to end	Night	2 4 1 3 3 2 3 4 5% 6% 67%	1520
July	1st to 10th	Night	1 1 2 2 2 2 2 3 4 81%	2540
	11th to 20th	Night	1 1 1 3 2 3 3 3 4 6% 72%	2540
	21st to end	Night	2 2 1 4 3 4 5% 4 6% 5% 64%	2761
August	1st to 10th	Night	3 3 2 5% 2 4 5% 3 6% 6% 61%	2688
	11th to 20th	Night	2 1 1 2 2 2 3 2 3 5% 76%	2931
	21st to end	Night	3 3 1 3 2 2 2 2 3 3 77%	3498
September	1st to 10th	Night	2 3 1 3 2 2 2 3 3 4 74%	1900
	11th to 20th	Night	4 5% 2 4 3 3 4 3 4 5% 64%	2047
	21st to end	Night	5% 4 1 3 2 3 3 2 4 6% 68%	2090
October	1st to 10th	Night	4 4 2 4 2 2 2 2 3 4 71%	3490
	11th to 20th	Night	5% 5% 1 4 3 3 3 3 4 6% 63%	3869
	21st to end	Night	6% 6% 3 7% 4 4 5% 4 7% 8% 45%	4457
November	1st to 10th	Night	9% 10% 3 7% 4 4 4 4 6% 7% 42%	2535
	11th to 20th	Night	11% 11% 3 6% 4 5% 4 4 6% 8% 39%	2600
	21st to end	Night	8% 10% 3 7% 6% 5% 4 4 5% 6% 42%	2625
December	1st to 10th	Night	6% 8% 3 6% 3 3 3 3 4 8% 54%	4560
	11th to 20th	Night	10% 17% 5% 10% 5% 5% 5% 5% 6% 8% 24%	5176
	21st to end	Night	12% 13% 5% 11% 6% 5% 5% 4 6% 7% 27%	6952

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	56% 12% 11% 14% 6%	3639
	11th to 20th	Day	46% 10% 11% 23% 10% 1	3640
	21st to end	Day	44% 6% 10% 13% 18% 9%	4004
February	1st to 10th	Day	42% 9% 17% 19% 11% 1	1832
	11th to 20th	Day	50% 8% 14% 16% 9% 3	1960
	21st to end	Day	45% 8% 14% 20% 9% 4	1650
March	1st to 10th	Day	47% 8% 9% 21% 11% 4	4518
	11th to 20th	Day	37% 8% 12% 27% 15% 1	4734
	21st to end	Day	44% 10% 16% 18% 10% 2	5837
April	1st to 10th	Day	44% 7% 15% 17% 14% 2	2400
	11th to 20th	Day	37% 6% 11% 24% 16% 4	2372
	21st to end	Day	34% 8% 15% 26% 16% 1	2587
May	1st to 10th	Day	31% 9% 13% 23% 19% 3	4240
	11th to 20th	Day	23% 4 8% 27% 29% 8%	4347
	21st to end	Day	28% 9% 11% 30% 20% 2	4887
June	1st to 10th	Day	34% 8% 11% 26% 18% 2	2660
	11th to 20th	Day	25% 5% 8% 24% 27% 11%	2660
	21st to end	Day	15% 4 6% 18% 35% 22%	2660
July	1st to 10th	Day	9% 2 3 7% 18% 60%	4351
	11th to 20th	Day	17% 3 2 6% 22% 50%	4345
	21st to end	Day	17% 4 2 7% 31% 39%	4639
August	1st to 10th	Day	23% 4 3 9% 21% 40%	4230
	11th to 20th	Day	10% 2 3 10% 30% 45%	3947
	21st to end	Day	15% 3 2 12% 33% 36%	4179
September	1st to 10th	Day	14% 3 4 12% 29% 38%	2280
	11th to 20th	Day	22% 4 5% 20% 27% 22%	2132
	21st to end	Day	21% 4 6% 19% 33% 17%	2090
October	1st to 10th	Day	22% 3 4 15% 36% 20%	3490
	11th to 20th	Day	27% 4 7% 27% 28% 7%	3062
	21st to end	Day	33% 6% 8% 26% 22% 5%	3101
November	1st to 10th	Day	43% 6% 10% 19% 17% 4	1764
	11th to 20th	Day	42% 8% 13% 24% 12% 2	1800
	21st to end	Day	40% 7% 12% 24% 14% 2	1772
December	1st to 10th	Day	30% 7% 9% 27% 26% 2	2620
	11th to 20th	Day	51% 8% 17% 17% 7% 1	3028
	21st to end	Day	52% 10% 13% 17% 7%	4004
January	1st to 10th	Night	52% 9% 13% 19% 7% 1	6306
	11th to 20th	Night	44% 8% 10% 22% 13% 3	6320
	21st to end	Night	41% 7% 10% 14% 16% 11%	6952
February	1st to 10th	Night	46% 8% 13% 22% 8% 2	2565
	11th to 20th	Night	41% 7% 17% 19% 12% 4	2339
	21st to end	Night	42% 10% 16% 20% 9% 3	1980
March	1st to 10th	Night	42% 7% 10% 18% 16% 7%	5376
	11th to 20th	Night	38% 6% 8% 27% 20% 1	5264
	21st to end	Night	36% 12% 18% 23% 10% 1	5123
April	1st to 10th	Night	40% 6% 13% 23% 15% 3	2000
	11th to 20th	Night	32% 7% 13% 26% 18% 4	1979
	21st to end	Night	31% 7% 16% 28% 17% 2	1811
May	1st to 10th	Night	29% 8% 10% 28% 22% 4	2950
	11th to 20th	Night	18% 6% 9% 27% 32% 8%	2770
	21st to end	Night	25% 6% 11% 28% 27% 2	2805
June	1st to 10th	Night	35% 6% 13% 26% 19% 1	1520
	11th to 20th	Night	23% 5% 8% 25% 29% 10%	1520
	21st to end	Night	17% 3 5% 20% 34% 20%	1520
July	1st to 10th	Night	8% 3 3 8% 19% 59%	2500
	11th to 20th	Night	13% 3 1 7% 22% 54%	2492
	21st to end	Night	19% 5% 2 8% 31% 36%	2674
August	1st to 10th	Night	23% 4 2 10% 24% 37%	2680
	11th to 20th	Night	13% 3 2 10% 26% 47%	2958
	21st to end	Night	14% 2 2 15% 31% 36%	3498
September	1st to 10th	Night	15% 3 3 9% 33% 38%	1900
	11th to 20th	Night	21% 4 6% 20% 24% 24%	2047
	21st to end	Night	18% 3 4 19% 35% 20%	2090
October	1st to 10th	Night	19% 2 5% 15% 32% 27%	3490
	11th to 20th	Night	22% 4 6% 24% 34% 10%	3869
	21st to end	Night	33% 5% 9% 24% 25% 5%	4457
November	1st to 10th	Night	37% 6% 11% 21% 19% 5%	2535
	11th to 20th	Night	41% 7% 12% 24% 16% 1	2600
	21st to end	Night	40% 5% 13% 20% 17% 4	2625
December	1st to 10th	Night	29% 5% 10% 28% 26% 2	4560
	11th to 20th	Night	54% 8% 12% 17% 9% 1	5176
	21st to end	Night	52% 9% 13% 18% 7% 1	6952

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	18% 10% 26% 27% 16% 5%	200
	11th to 20th	Day	8% 10% 30% 28% 15% 10%	200
	21st to end	Day	11% 6% 23% 32% 19% 9%	220
February	1st to 10th	Day	11% 13% 33% 23% 16% 4	386
	11th to 20th	Day	11% 15% 30% 29% 13% 2	495
	21st to end	Day	10% 15% 30% 29% 13% 3	414
March	1st to 10th	Day	13% 14% 31% 28% 14%	500
	11th to 20th	Day	8% 11% 30% 31% 17% 3	500
	21st to end	Day	14% 12% 29% 29% 15% 1	550
April	1st to 10th	Day	13% 12% 23% 28% 19% 4	500
	11th to 20th	Day	11% 12% 32% 24% 15% 6%	492
	21st to end	Day	10% 10% 28% 27% 20% 6%	500
May	1st to 10th	Day	6% 13% 29% 28% 18% 7%	503
	11th to 20th	Day	17% 8% 26% 24% 15% 10%	528
	21st to end	Day	10% 7% 20% 27% 23% 13%	550
June	1st to 10th	Day	10% 9% 21% 30% 20% 10%	490
	11th to 20th	Day	8% 12% 30% 29% 16% 5%	490
	21st to end	Day	4 7% 25% 34% 20% 10%	490
July	1st to 10th	Day	3 5% 25% 36% 25% 7%	486
	11th to 20th	Day	3 5% 24% 35% 22% 11%	484
	21st to end	Day	5% 4 21% 34% 24% 12%	531
August	1st to 10th	Day	7% 3 22% 33% 23% 12%	487
	11th to 20th	Day	3 3 23% 34% 23% 13%	477
	21st to end	Day	3 4 25% 29% 24% 14%	539
September	1st to 10th	Day	4 5% 20% 28% 28% 14%	490
	11th to 20th	Day	5% 8% 24% 29% 23% 11%	490
	21st to end	Day	7% 8% 20% 32% 24% 9%	490
October	1st to 10th	Day	9% 11% 19% 26% 23% 13%	490
	11th to 20th	Day	9% 10% 23% 24% 25% 10%	428
	21st to end	Day	8% 11% 28% 31% 19% 4	330
November	1st to 10th	Day	11% 8% 29% 29% 21% 2	300
	11th to 20th	Day	14% 10% 23% 30% 19% 4	300
	21st to end	Day	10% 8% 22% 30% 23% 6%	285
December	1st to 10th	Day	15% 11% 19% 26% 17% 14%	200
	11th to 20th	Day	16% 9% 29% 30% 15% 4	200
	21st to end	Day	19% 12% 24% 26% 16% 3	220
January	1st to 10th	Night	14% 9% 23% 31% 19% 5%	800
	11th to 20th	Night	12% 9% 20% 34% 21% 4	800
	21st to end	Night	13% 6% 19% 34% 23% 5%	880
February	1st to 10th	Night	12% 8% 26% 33% 17% 4	800
	11th to 20th	Night	10% 8% 25% 37% 17% 2	784
	21st to end	Night	8% 9% 25% 40% 14% 2	660
March	1st to 10th	Night	11% 8% 26% 37% 16% 2	800
	11th to 20th	Night	11% 8% 21% 36% 20% 3	800
	21st to end	Night	13% 8% 27% 35% 15% 1	880
April	1st to 10th	Night	12% 8% 23% 36% 19% 3	800
	11th to 20th	Night	9% 9% 23% 38% 16% 4	791
	21st to end	Night	10% 7% 22% 39% 20% 3	611
May	1st to 10th	Night	7% 8% 27% 37% 20% 1	600
	11th to 20th	Night	10% 6% 19% 35% 26% 4	503
	21st to end	Night	10% 6% 17% 36% 26% 5%	422
June	1st to 10th	Night	8% 5% 17% 42% 24% 4	380
	11th to 20th	Night	6% 7% 19% 44% 23% 2	380
	21st to end	Night	3 4 16% 50% 25% 2	380
July	1st to 10th	Night	1 1 9% 58% 28% 3	370
	11th to 20th	Night	3 1 11% 57% 27% 1	368
	21st to end	Night	4 7% 53% 33% 2	416
August	1st to 10th	Night	6% 2 11% 49% 31% 2	472
	11th to 20th	Night	2 2 14% 45% 34% 3	632
	21st to end	Night	3 2 11% 47% 32% 4	836
September	1st to 10th	Night	4 1 12% 45% 31% 7%	760
	11th to 20th	Night	5% 1 12% 39% 35% 8%	760
	21st to end	Night	8% 3 13% 36% 31% 10%	760
October	1st to 10th	Night	9% 3 16% 38% 28% 6%	760
	11th to 20th	Night	8% 7% 16% 34% 28% 7%	760
	21st to end	Night	7% 6% 17% 40% 23% 7%	836
November	1st to 10th	Night	13% 7% 19% 33% 24% 4	780
	11th to 20th	Night	15% 8% 20% 36% 19% 3	800
	21st to end	Night	10% 9% 20% 35% 21% 6%	800
December	1st to 10th	Night	13% 7% 20% 38% 20% 4	800
	11th to 20th	Night	16% 9% 19% 36% 17% 3	800
	21st to end	Night	17% 10% 26% 33% 11% 2	880

Page generated at 2025-05-23 07:21:00. Version ac07

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