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 2024-11-02.

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% 8% 3 7% 4 4 4 3 5% 6% 51%	101251
	Night	6% 9% 3 7% 4 4 4 3 5% 6% 48%	97890
Transparency	Day	31% 7% 9% 18% 19% 16%	100995
	Night	34% 7% 11% 19% 18% 12%	97735
Seeing	Day	9% 9% 25% 30% 20% 8%	14577
	Night	10% 6% 19% 39% 23% 4	23889

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% 18% 7% 17% 7% 5% 5% 3 6% 6% 20%	2539
	11th to 20th	Day	8% 18% 6% 14% 6% 5% 4 4 4 6% 27%	2540
	21st to end	Day	10% 19% 5% 11% 5% 5% 4 3 5% 6% 26%	2794
February	1st to 10th	Day	6% 13% 4 9% 5% 5% 4 4 6% 8% 36%	1740
	11th to 20th	Day	6% 14% 6% 11% 5% 5% 4 3 5% 5% 34%	1850
	21st to end	Day	5% 14% 5% 11% 6% 4 4 4 5% 7% 34%	1570
March	1st to 10th	Day	6% 16% 6% 10% 6% 5% 5% 4 6% 7% 29%	3138
	11th to 20th	Day	4 10% 3 9% 3 3 4 4 4 5% 52%	3302
	21st to end	Day	5% 12% 6% 12% 6% 6% 5% 5% 6% 9% 28%	4072
April	1st to 10th	Day	10% 12% 3 9% 5% 4 4 4 6% 7% 36%	2280
	11th to 20th	Day	6% 12% 3 7% 5% 5% 4 3 6% 7% 43%	2249
	21st to end	Day	6% 9% 3 6% 4 3 4 4 7% 8% 45%	2457
May	1st to 10th	Day	5% 12% 4 7% 4 4 4 4 6% 6% 43%	4110
	11th to 20th	Day	6% 4 1 5% 3 3 3 3 4 5% 64%	4209
	21st to end	Day	6% 8% 3 5% 4 4 4 3 6% 7% 50%	4813
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	7% 7% 3 6% 3 3 4 2 4 5% 56%	2090
	11th to 20th	Day	7% 7% 2 5% 3 3 3 3 4 7% 56%	1852
	21st to end	Day	6% 7% 2 6% 3 4 5% 3 6% 6% 51%	1881
November	1st to 10th	Day	9% 13% 4 7% 5% 3 4 3 5% 6% 41%	1683
	11th to 20th	Day	11% 10% 3 6% 5% 5% 4 4 6% 8% 39%	1710
	21st to end	Day	7% 13% 4 9% 3 3 4 5% 6% 8% 39%	1684
December	1st to 10th	Day	10% 13% 4 8% 6% 4 4 4 5% 9% 34%	1520
	11th to 20th	Day	10% 14% 4 11% 6% 4 4 4 7% 8% 29%	1928
	21st to end	Day	7% 13% 6% 11% 6% 4 5% 4 6% 8% 30%	2794
January	1st to 10th	Night	6% 18% 7% 13% 5% 5% 4 4 6% 6% 27%	4406
	11th to 20th	Night	11% 22% 6% 12% 5% 3 3 2 4 6% 27%	4420
	21st to end	Night	8% 18% 5% 10% 5% 5% 4 4 5% 7% 29%	4862
February	1st to 10th	Night	7% 12% 4 11% 6% 5% 4 4 5% 7% 35%	2437
	11th to 20th	Night	7% 12% 5% 7% 4 5% 4 4 5% 7% 39%	2218
	21st to end	Night	5% 13% 5% 9% 6% 5% 5% 5% 6% 7% 34%	1884
March	1st to 10th	Night	6% 16% 5% 9% 4 4 5% 4 6% 7% 35%	3736
	11th to 20th	Night	6% 9% 3 7% 4 4 3 3 5% 4 53%	3676
	21st to end	Night	7% 12% 4 9% 5% 5% 5% 5% 7% 8% 34%	3566
April	1st to 10th	Night	9% 10% 3 8% 5% 5% 4 3 5% 7% 42%	1900
	11th to 20th	Night	6% 10% 3 6% 5% 3 4 4 5% 6% 48%	1879
	21st to end	Night	6% 8% 2 7% 4 4 4 4 6% 7% 48%	1721
May	1st to 10th	Night	7% 9% 3 7% 3 3 4 4 5% 7% 47%	2860
	11th to 20th	Night	4 3 1 3 3 3 4 3 5% 6% 65%	2685
	21st to end	Night	6% 6% 2 5% 3 3 4 3 5% 7% 55%	2762
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	7% 6% 2 4 3 2 3 2 4 5% 61%	2090
	11th to 20th	Night	7% 5% 1 4 3 3 4 3 4 6% 60%	2325
	21st to end	Night	6% 6% 2 7% 4 4 4 4 6% 8% 49%	2717
November	1st to 10th	Night	9% 11% 3 7% 4 4 4 4 6% 7% 42%	2430
	11th to 20th	Night	11% 11% 3 6% 4 5% 4 4 6% 7% 39%	2470
	21st to end	Night	7% 10% 3 8% 6% 5% 4 4 5% 7% 42%	2493
December	1st to 10th	Night	10% 12% 4 8% 4 4 4 4 5% 8% 36%	2660
	11th to 20th	Night	9% 15% 4 11% 5% 5% 5% 4 6% 8% 27%	3276
	21st to end	Night	9% 12% 5% 11% 6% 5% 4 4 6% 7% 31%	4862

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% 14% 13% 15% 2 1	2539
	11th to 20th	Day	55% 12% 13% 13% 6% 1	2540
	21st to end	Day	58% 9% 15% 12% 5% 1	2794
February	1st to 10th	Day	42% 10% 18% 20% 9% 1	1740
	11th to 20th	Day	49% 8% 14% 17% 9% 3	1860
	21st to end	Day	47% 9% 14% 20% 8% 2	1570
March	1st to 10th	Day	48% 10% 12% 18% 11% 1	3138
	11th to 20th	Day	29% 9% 14% 32% 15% 1	3302
	21st to end	Day	46% 12% 15% 20% 7% 1	4072
April	1st to 10th	Day	45% 7% 16% 17% 14% 2	2280
	11th to 20th	Day	39% 6% 12% 25% 14% 4	2252
	21st to end	Day	33% 8% 15% 26% 16% 1	2457
May	1st to 10th	Day	32% 10% 14% 23% 18% 3	4110
	11th to 20th	Day	22% 4 8% 27% 30% 8%	4212
	21st to end	Day	29% 9% 11% 30% 20% 2	4814
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	31% 4 7% 20% 24% 14%	2090
	11th to 20th	Day	27% 4 8% 30% 23% 8%	1852
	21st to end	Day	31% 6% 12% 25% 21% 5%	1881
November	1st to 10th	Day	43% 6% 11% 19% 17% 4	1683
	11th to 20th	Day	41% 8% 14% 24% 12% 2	1710
	21st to end	Day	41% 7% 13% 22% 15% 2	1684
December	1st to 10th	Day	46% 10% 15% 19% 7% 3	1520
	11th to 20th	Day	50% 8% 19% 12% 10% 1	1928
	21st to end	Day	48% 11% 14% 18% 9% 1	2794
January	1st to 10th	Night	52% 10% 16% 17% 4 1	4406
	11th to 20th	Night	55% 10% 12% 13% 7% 2	4420
	21st to end	Night	55% 10% 14% 14% 5% 2	4862
February	1st to 10th	Night	45% 9% 14% 23% 8% 2	2437
	11th to 20th	Night	40% 7% 17% 20% 12% 4	2219
	21st to end	Night	43% 10% 17% 21% 8% 2	1884
March	1st to 10th	Night	43% 9% 13% 18% 15% 2	3736
	11th to 20th	Night	31% 5% 11% 29% 22% 2	3676
	21st to end	Night	40% 12% 20% 22% 6% 1	3566
April	1st to 10th	Night	40% 6% 13% 23% 14% 3	1900
	11th to 20th	Night	33% 7% 13% 26% 16% 3	1879
	21st to end	Night	31% 6% 16% 28% 17% 2	1721
May	1st to 10th	Night	29% 8% 10% 28% 21% 4	2860
	11th to 20th	Night	17% 5% 10% 27% 33% 8%	2685
	21st to end	Night	26% 6% 12% 28% 27% 1	2762
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	26% 3 7% 22% 26% 15%	2090
	11th to 20th	Night	24% 5% 8% 25% 29% 9%	2325
	21st to end	Night	30% 6% 13% 23% 23% 5%	2717
November	1st to 10th	Night	38% 6% 11% 21% 19% 5%	2430
	11th to 20th	Night	40% 7% 12% 24% 17% 1	2470
	21st to end	Night	41% 5% 13% 20% 17% 4	2493
December	1st to 10th	Night	44% 8% 17% 19% 9% 3	2660
	11th to 20th	Night	51% 8% 14% 15% 10% 1	3276
	21st to end	Night	47% 10% 15% 19% 8% 1	4862

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% 9% 24% 28% 17% 5%	180
	11th to 20th	Day	9% 9% 27% 30% 14% 11%	180
	21st to end	Day	11% 7% 21% 34% 18% 9%	198
February	1st to 10th	Day	10% 13% 33% 23% 17% 4	354
	11th to 20th	Day	10% 14% 30% 30% 14% 2	455
	21st to end	Day	10% 15% 30% 29% 14% 3	382
March	1st to 10th	Day	13% 13% 31% 29% 13%	460
	11th to 20th	Day	7% 9% 30% 32% 17% 3	460
	21st to end	Day	14% 12% 29% 30% 15% 1	506
April	1st to 10th	Day	14% 12% 23% 27% 20% 4	460
	11th to 20th	Day	12% 12% 32% 25% 15% 5%	452
	21st to end	Day	10% 11% 27% 27% 20% 6%	460
May	1st to 10th	Day	6% 12% 30% 28% 17% 7%	463
	11th to 20th	Day	17% 7% 25% 24% 16% 11%	488
	21st to end	Day	11% 7% 19% 27% 23% 13%	529
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	12% 7% 30% 29% 21% 2	273
	11th to 20th	Day	12% 7% 22% 33% 21% 4	270
	21st to end	Day	9% 9% 21% 32% 23% 5%	257
December	1st to 10th	Day	16% 11% 19% 27% 16% 11%	180
	11th to 20th	Day	16% 8% 28% 29% 15% 4	180
	21st to end	Day	16% 12% 24% 27% 18% 3	198
January	1st to 10th	Night	14% 8% 22% 31% 20% 5%	760
	11th to 20th	Night	13% 9% 19% 34% 21% 5%	760
	21st to end	Night	14% 6% 18% 34% 22% 6%	836
February	1st to 10th	Night	11% 8% 26% 33% 18% 4	760
	11th to 20th	Night	10% 7% 25% 38% 18% 3	744
	21st to end	Night	8% 9% 25% 41% 14% 2	628
March	1st to 10th	Night	11% 7% 26% 37% 16% 2	760
	11th to 20th	Night	11% 7% 21% 36% 21% 4	760
	21st to end	Night	13% 9% 27% 35% 15% 1	836
April	1st to 10th	Night	13% 8% 23% 35% 19% 3	760
	11th to 20th	Night	9% 9% 23% 38% 16% 5%	751
	21st to end	Night	10% 7% 22% 39% 20% 3	581
May	1st to 10th	Night	7% 8% 27% 37% 20% 1	570
	11th to 20th	Night	9% 6% 18% 36% 27% 4	478
	21st to end	Night	10% 6% 17% 35% 26% 5%	411
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% 6% 19% 33% 24% 4	748
	11th to 20th	Night	15% 6% 20% 36% 20% 3	760
	21st to end	Night	10% 8% 20% 35% 22% 6%	760
December	1st to 10th	Night	13% 7% 20% 38% 18% 3	760
	11th to 20th	Night	16% 9% 19% 35% 18% 3	760
	21st to end	Night	17% 9% 27% 34% 11% 2	836

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