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 2026-09-29.

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	5% 7% 2 6% 4 4 4 3 5% 6% 54%	157700
	Night	5% 8% 3 6% 4 4 4 3 5% 7% 51%	151115
Transparency	Day	30% 6% 8% 19% 22% 16%	152520
	Night	32% 6% 9% 19% 21% 13%	147291
Seeing	Day	9% 9% 26% 29% 20% 8%	17021
	Night	9% 6% 19% 39% 22% 4	26271

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	7% 18% 6% 15% 6% 4 5% 4 6% 7% 22%	4722
	11th to 20th	Day	4 10% 4 10% 4 4 3 3 4 5% 49%	4740
	21st to end	Day	7% 12% 4 8% 4 5% 4 3 5% 6% 42%	5187
February	1st to 10th	Day	6% 13% 4 9% 5% 5% 4 4 6% 7% 37%	1924
	11th to 20th	Day	7% 14% 6% 11% 6% 5% 4 3 5% 6% 33%	2050
	21st to end	Day	6% 13% 4 11% 6% 4 4 4 5% 8% 35%	1730
March	1st to 10th	Day	5% 17% 5% 10% 6% 5% 5% 4 5% 7% 32%	4618
	11th to 20th	Day	4 11% 4 11% 5% 4 4 4 4 6% 44%	4838
	21st to end	Day	4 13% 5% 11% 6% 5% 5% 4 6% 8% 33%	5966
April	1st to 10th	Day	9% 11% 3 9% 5% 4 4 4 6% 8% 37%	2520
	11th to 20th	Day	6% 11% 3 7% 4 5% 4 4 6% 7% 44%	2489
	21st to end	Day	6% 9% 3 6% 4 4 4 4 6% 8% 46%	2716
May	1st to 10th	Day	4 7% 3 5% 3 3 3 3 5% 6% 57%	7626
	11th to 20th	Day	5% 6% 2 5% 3 3 3 3 5% 6% 59%	7851
	21st to end	Day	4 5% 2 5% 4 4 4 3 5% 6% 57%	8992
June	1st to 10th	Day	9% 7% 2 5% 4 4 5% 4 6% 8% 46%	2940
	11th to 20th	Day	6% 5% 2 4 3 3 4 3 5% 7% 58%	2940
	21st to end	Day	3 3 1 3 2 3 3 3 4 6% 69%	2940
July	1st to 10th	Day	1 1 1 2 2 2 3 2 4 5% 77%	8219
	11th to 20th	Day	2 2 1 3 3 3 3 3 4 5% 71%	8220
	21st to end	Day	3 3 1 4 3 4 4 4 5% 6% 64%	8922
August	1st to 10th	Day	2 3 1 3 2 3 3 3 4 6% 71%	7831
	11th to 20th	Day	2 2 1 3 3 3 3 3 4 6% 71%	7341
	21st to end	Day	5% 4 2 4 3 4 4 3 5% 6% 61%	7750
September	1st to 10th	Day	3 3 1 4 2 2 3 3 4 6% 70%	2520
	11th to 20th	Day	4 4 1 4 3 4 3 3 3 5% 65%	2356
	21st to end	Day	5% 6% 2 4 2 2 3 2 4 6% 64%	2289
October	1st to 10th	Day	4 5% 2 5% 2 2 3 2 3 4 68%	3600
	11th to 20th	Day	8% 7% 2 4 3 3 3 3 4 6% 58%	3159
	21st to end	Day	4 8% 3 6% 4 4 5% 4 7% 8% 46%	3200
November	1st to 10th	Day	9% 13% 4 8% 5% 3 4 3 5% 6% 41%	1854
	11th to 20th	Day	11% 10% 3 6% 5% 5% 4 4 5% 8% 38%	1890
	21st to end	Day	7% 13% 3 9% 3 3 4 5% 6% 8% 40%	1860
December	1st to 10th	Day	6% 8% 3 6% 4 3 3 3 4 8% 52%	2700
	11th to 20th	Day	12% 13% 3 9% 5% 5% 4 4 7% 7% 30%	3108
	21st to end	Day	13% 15% 5% 10% 5% 4 5% 4 6% 7% 27%	4092
January	1st to 10th	Night	8% 19% 6% 11% 5% 4 4 3 5% 6% 27%	8172
	11th to 20th	Night	6% 12% 4 8% 3 3 3 2 4 5% 50%	8220
	21st to end	Night	5% 11% 4 7% 4 4 5% 4 6% 8% 44%	8994
February	1st to 10th	Night	8% 12% 4 10% 5% 5% 4 4 5% 7% 35%	2693
	11th to 20th	Night	7% 12% 5% 8% 4 5% 4 5% 6% 8% 37%	2458
	21st to end	Night	6% 12% 5% 8% 5% 5% 5% 5% 6% 7% 35%	2076
March	1st to 10th	Night	6% 17% 4 8% 4 4 4 4 5% 6% 38%	5496
	11th to 20th	Night	7% 11% 4 8% 5% 4 4 3 5% 6% 43%	5380
	21st to end	Night	5% 11% 3 7% 5% 5% 5% 5% 7% 9% 38%	5236
April	1st to 10th	Night	8% 9% 2 8% 5% 5% 4 4 6% 7% 41%	2100
	11th to 20th	Night	6% 10% 3 6% 5% 4 4 3 5% 6% 49%	2079
	21st to end	Night	6% 8% 2 7% 4 4 4 4 6% 7% 49%	1902
May	1st to 10th	Night	5% 6% 2 4 2 2 3 2 4 7% 62%	5321
	11th to 20th	Night	3 5% 2 5% 3 3 4 3 5% 6% 60%	5021
	21st to end	Night	4 5% 2 4 3 3 4 3 5% 7% 60%	5181
June	1st to 10th	Night	7% 6% 3 6% 5% 4 5% 4 5% 6% 49%	1680
	11th to 20th	Night	5% 5% 2 4 3 4 3 2 4 5% 63%	1680
	21st to end	Night	2 4 1 3 3 3 3 4 5% 6% 66%	1680
July	1st to 10th	Night	2 2 1 2 2 2 3 2 4 5% 76%	4740
	11th to 20th	Night	1 2 1 3 2 3 3 3 4 6% 71%	4740
	21st to end	Night	2 2 1 4 3 4 5% 5% 7% 7% 60%	5153
August	1st to 10th	Night	2 2 1 3 2 3 3 3 4 5% 72%	4976
	11th to 20th	Night	2 1 1 3 3 3 4 3 4 7% 71%	5523
	21st to end	Night	4 4 2 4 3 3 3 3 5% 7% 61%	6499
September	1st to 10th	Night	3 3 1 3 3 2 3 3 3 5% 71%	2100
	11th to 20th	Night	3 5% 2 4 3 3 3 3 4 5% 65%	2263
	21st to end	Night	5% 4 1 3 2 3 3 2 4 6% 67%	2288
October	1st to 10th	Night	5% 4 2 4 2 2 2 2 3 4 71%	3600
	11th to 20th	Night	5% 5% 1 4 3 3 3 3 4 6% 63%	3991
	21st to end	Night	6% 6% 3 7% 4 4 5% 4 6% 8% 46%	4600
November	1st to 10th	Night	9% 10% 3 7% 4 4 4 4 6% 7% 42%	2665
	11th to 20th	Night	11% 11% 3 6% 5% 5% 4 4 6% 8% 38%	2730
	21st to end	Night	8% 10% 3 7% 6% 5% 4 4 5% 7% 42%	2756
December	1st to 10th	Night	6% 8% 3 6% 3 3 3 3 4 8% 54%	4700
	11th to 20th	Night	10% 17% 5% 10% 5% 5% 5% 5% 6% 8% 25%	5316
	21st to end	Night	12% 13% 5% 11% 6% 5% 5% 4 6% 7% 27%	7106

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	55% 11% 15% 14% 5%	4723
	11th to 20th	Day	36% 8% 8% 22% 22% 4	4740
	21st to end	Day	43% 6% 10% 13% 21% 8%	5187
February	1st to 10th	Day	41% 9% 17% 20% 12% 1	1924
	11th to 20th	Day	50% 8% 14% 16% 9% 3	2060
	21st to end	Day	46% 8% 13% 20% 9% 4	1730
March	1st to 10th	Day	47% 8% 9% 21% 11% 4	4618
	11th to 20th	Day	37% 8% 13% 26% 15% 2	4838
	21st to end	Day	44% 10% 15% 18% 10% 2	5966
April	1st to 10th	Day	44% 7% 15% 18% 15% 2	2520
	11th to 20th	Day	38% 6% 11% 24% 17% 4	2492
	21st to end	Day	34% 8% 14% 25% 17% 2	2716
May	1st to 10th	Day	23% 6% 9% 24% 33% 6%	7626
	11th to 20th	Day	25% 4 6% 26% 30% 8%	7854
	21st to end	Day	25% 6% 7% 28% 28% 5%	8994
June	1st to 10th	Day	33% 8% 10% 25% 21% 4	2940
	11th to 20th	Day	24% 5% 8% 24% 28% 13%	2940
	21st to end	Day	16% 4 6% 19% 34% 21%	2940
July	1st to 10th	Day	11% 2 2 11% 24% 50%	8151
	11th to 20th	Day	16% 3 2 8% 23% 49%	8145
	21st to end	Day	19% 4 3 11% 28% 35%	8723
August	1st to 10th	Day	17% 3 2 7% 19% 51%	6200
	11th to 20th	Day	18% 3 3 15% 28% 33%	5788
	21st to end	Day	21% 3 3 16% 30% 26%	6077
September	1st to 10th	Day	16% 3 4 13% 28% 35%	2520
	11th to 20th	Day	21% 4 5% 20% 29% 21%	2356
	21st to end	Day	22% 3 5% 19% 33% 18%	2289
October	1st to 10th	Day	22% 3 4 15% 36% 20%	3600
	11th to 20th	Day	27% 3 7% 27% 27% 7%	3159
	21st to end	Day	33% 5% 8% 27% 22% 5%	3200
November	1st to 10th	Day	43% 6% 10% 21% 17% 4	1854
	11th to 20th	Day	42% 8% 14% 24% 11% 1	1890
	21st to end	Day	40% 7% 13% 24% 14% 2	1860
December	1st to 10th	Day	31% 7% 9% 26% 25% 2	2700
	11th to 20th	Day	51% 7% 17% 17% 7% 1	3108
	21st to end	Day	52% 10% 13% 18% 7%	4092
January	1st to 10th	Night	52% 10% 14% 19% 5% 1	8172
	11th to 20th	Night	35% 6% 8% 20% 23% 8%	8220
	21st to end	Night	39% 6% 10% 14% 19% 11%	8994
February	1st to 10th	Night	46% 8% 13% 22% 9% 2	2693
	11th to 20th	Night	42% 7% 17% 20% 11% 3	2459
	21st to end	Night	42% 10% 16% 20% 9% 3	2076
March	1st to 10th	Night	42% 7% 10% 19% 16% 7%	5496
	11th to 20th	Night	37% 6% 9% 26% 20% 2	5380
	21st to end	Night	36% 12% 18% 23% 10% 1	5236
April	1st to 10th	Night	40% 6% 13% 24% 15% 3	2100
	11th to 20th	Night	33% 7% 12% 25% 19% 3	2079
	21st to end	Night	31% 6% 15% 28% 18% 2	1902
May	1st to 10th	Night	20% 5% 7% 23% 38% 7%	5319
	11th to 20th	Night	22% 4 6% 27% 34% 7%	5021
	21st to end	Night	23% 4 8% 28% 32% 5%	5182
June	1st to 10th	Night	33% 6% 11% 25% 21% 3	1680
	11th to 20th	Night	22% 5% 7% 24% 31% 11%	1680
	21st to end	Night	17% 4 5% 20% 34% 20%	1680
July	1st to 10th	Night	12% 3 2 11% 24% 49%	4700
	11th to 20th	Night	15% 2 2 8% 20% 52%	4692
	21st to end	Night	20% 4 3 14% 25% 33%	5040
August	1st to 10th	Night	17% 3 1 8% 21% 51%	3935
	11th to 20th	Night	18% 3 3 14% 26% 36%	4348
	21st to end	Night	22% 2 3 17% 31% 25%	5092
September	1st to 10th	Night	17% 2 3 10% 32% 35%	2100
	11th to 20th	Night	21% 4 5% 20% 26% 23%	2263
	21st to end	Night	19% 3 4 19% 35% 21%	2288
October	1st to 10th	Night	19% 2 5% 15% 32% 27%	3600
	11th to 20th	Night	22% 4 6% 24% 34% 10%	3991
	21st to end	Night	33% 5% 9% 24% 25% 5%	4600
November	1st to 10th	Night	37% 6% 12% 22% 19% 5%	2665
	11th to 20th	Night	41% 7% 13% 24% 15%	2730
	21st to end	Night	40% 5% 13% 21% 17% 4	2756
December	1st to 10th	Night	29% 5% 11% 28% 25% 2	4700
	11th to 20th	Night	54% 8% 12% 17% 9% 1	5316
	21st to end	Night	52% 9% 13% 18% 7% 1	7106

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	17% 11% 26% 26% 15% 4	220
	11th to 20th	Day	7% 9% 28% 28% 17% 10%	220
	21st to end	Day	10% 6% 24% 33% 19% 8%	242
February	1st to 10th	Day	10% 14% 32% 23% 17% 4	418
	11th to 20th	Day	10% 15% 31% 29% 13% 2	535
	21st to end	Day	11% 15% 31% 28% 12% 3	446
March	1st to 10th	Day	12% 15% 32% 27% 13%	540
	11th to 20th	Day	8% 13% 31% 30% 16% 3	540
	21st to end	Day	13% 12% 30% 28% 15% 1	594
April	1st to 10th	Day	13% 13% 22% 27% 20% 5%	540
	11th to 20th	Day	12% 11% 32% 25% 14% 5%	532
	21st to end	Day	9% 11% 29% 26% 20% 5%	540
May	1st to 10th	Day	6% 12% 28% 28% 19% 7%	543
	11th to 20th	Day	17% 9% 26% 24% 14% 9%	568
	21st to end	Day	10% 7% 21% 28% 22% 13%	617
June	1st to 10th	Day	9% 10% 22% 31% 19% 9%	570
	11th to 20th	Day	8% 11% 31% 30% 16% 5%	570
	21st to end	Day	4 6% 25% 34% 21% 9%	570
July	1st to 10th	Day	3 5% 27% 34% 24% 8%	566
	11th to 20th	Day	2 5% 24% 35% 23% 10%	564
	21st to end	Day	5% 4 21% 33% 24% 12%	619
August	1st to 10th	Day	6% 3 23% 33% 23% 12%	567
	11th to 20th	Day	3 4 23% 35% 24% 12%	557
	21st to end	Day	4 5% 23% 29% 25% 14%	627
September	1st to 10th	Day	5% 5% 22% 29% 26% 13%	570
	11th to 20th	Day	5% 7% 24% 29% 24% 12%	570
	21st to end	Day	6% 7% 19% 33% 25% 10%	563
October	1st to 10th	Day	8% 11% 20% 26% 22% 12%	530
	11th to 20th	Day	10% 10% 24% 24% 24% 9%	465
	21st to end	Day	9% 10% 28% 30% 21% 3	363
November	1st to 10th	Day	11% 8% 30% 29% 20% 2	330
	11th to 20th	Day	13% 10% 23% 31% 19% 4	330
	21st to end	Day	9% 9% 23% 30% 22% 6%	313
December	1st to 10th	Day	14% 11% 21% 25% 16% 13%	220
	11th to 20th	Day	16% 9% 26% 30% 15% 4	220
	21st to end	Day	20% 13% 24% 24% 17% 2	242
January	1st to 10th	Night	14% 9% 23% 31% 19% 4	840
	11th to 20th	Night	11% 8% 19% 35% 21% 5%	840
	21st to end	Night	13% 6% 19% 36% 22% 5%	924
February	1st to 10th	Night	12% 8% 26% 33% 17% 4	840
	11th to 20th	Night	10% 8% 26% 37% 17% 2	824
	21st to end	Night	8% 9% 26% 40% 14% 2	692
March	1st to 10th	Night	11% 8% 27% 37% 16% 1	840
	11th to 20th	Night	11% 8% 23% 36% 20% 3	840
	21st to end	Night	12% 9% 27% 36% 15% 1	924
April	1st to 10th	Night	12% 8% 22% 36% 20% 3	840
	11th to 20th	Night	9% 9% 23% 39% 16% 4	831
	21st to end	Night	10% 7% 22% 39% 19% 3	642
May	1st to 10th	Night	7% 8% 27% 37% 20% 1	630
	11th to 20th	Night	9% 6% 20% 36% 26% 3	529
	21st to end	Night	9% 6% 18% 36% 26% 5%	455
June	1st to 10th	Night	8% 5% 17% 42% 25% 3	420
	11th to 20th	Night	5% 6% 19% 45% 22% 2	420
	21st to end	Night	3 4 16% 51% 25% 2	420
July	1st to 10th	Night	2 1 10% 57% 27% 3	410
	11th to 20th	Night	2 1 11% 59% 26% 1	408
	21st to end	Night	3 7% 53% 34% 2	460
August	1st to 10th	Night	5% 2 11% 49% 31% 2	522
	11th to 20th	Night	2 2 14% 47% 33% 3	700
	21st to end	Night	4 2 12% 47% 31% 4	924
September	1st to 10th	Night	4 2 13% 46% 30% 6%	840
	11th to 20th	Night	5% 2 13% 40% 33% 7%	840
	21st to end	Night	8% 3 13% 36% 31% 9%	832
October	1st to 10th	Night	10% 3 17% 38% 27% 5%	800
	11th to 20th	Night	8% 7% 17% 35% 27% 7%	800
	21st to end	Night	7% 7% 17% 41% 23% 7%	880
November	1st to 10th	Night	12% 7% 20% 34% 24% 4	820
	11th to 20th	Night	14% 8% 20% 35% 20% 3	840
	21st to end	Night	9% 8% 20% 36% 21% 5%	840
December	1st to 10th	Night	12% 7% 20% 38% 19% 3	840
	11th to 20th	Night	15% 9% 19% 37% 16% 3	840
	21st to end	Night	18% 10% 27% 32% 11% 2	924

Page generated at 2026-09-26 02:18:38. Version ac07

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