Crater Lake National Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Crater Lake National Park 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	6% 10% 4 8% 4 3 3 3 4 5% 49%	101497
	Night	6% 11% 4 10% 5% 4 4 3 5% 5% 44%	97660
Transparency	Day	36% 5% 9% 18% 19% 11%	101243
	Night	40% 6% 10% 18% 17% 9%	97503
Seeing	Day	18% 16% 26% 24% 13% 3	14825
	Night	17% 11% 18% 31% 20% 3	23863

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% 17% 10% 18% 7% 5% 5% 4 4 4 20%	2539
	11th to 20th	Day	12% 18% 6% 13% 6% 6% 4 2 5% 4 24%	2573
	21st to end	Day	10% 23% 7% 10% 5% 4 4 3 5% 6% 22%	3146
February	1st to 10th	Day	10% 16% 6% 9% 5% 4 5% 5% 6% 7% 27%	1710
	11th to 20th	Day	6% 17% 6% 13% 6% 6% 3 3 4 7% 29%	1665
	21st to end	Day	6% 17% 8% 15% 6% 5% 4 4 4 5% 26%	1555
March	1st to 10th	Day	5% 19% 10% 17% 6% 4 3 2 3 4 27%	3280
	11th to 20th	Day	5% 14% 5% 8% 4 2 3 2 3 5% 48%	3490
	21st to end	Day	6% 22% 9% 14% 6% 5% 4 4 5% 6% 19%	3934
April	1st to 10th	Day	9% 19% 7% 12% 5% 5% 3 3 5% 6% 26%	2280
	11th to 20th	Day	8% 18% 5% 10% 5% 4 4 4 4 6% 30%	2249
	21st to end	Day	4 15% 5% 10% 5% 3 4 4 6% 7% 36%	2351
May	1st to 10th	Day	7% 12% 6% 9% 4 3 3 3 5% 5% 43%	4280
	11th to 20th	Day	5% 6% 2 5% 2 3 3 2 4 6% 61%	4377
	21st to end	Day	6% 9% 3 7% 4 3 4 3 5% 9% 47%	4813
June	1st to 10th	Day	9% 9% 3 7% 5% 5% 4 4 6% 7% 41%	2660
	11th to 20th	Day	4 6% 3 7% 4 4 4 3 4 6% 54%	2660
	21st to end	Day	4 4 1 4 3 2 3 3 4 5% 67%	2660
July	1st to 10th	Day	1 1 2 1 1 1 1 2 2 86%	4420
	11th to 20th	Day	2 2 1 2 2 2 3 2 3 3 78%	4420
	21st to end	Day	1 1 1 2 1 1 2 1 2 3 85%	4704
August	1st to 10th	Day	3 3 1 3 2 2 2 2 5% 5% 70%	4091
	11th to 20th	Day	2 2 1 3 3 3 3 3 3 5% 74%	4026
	21st to end	Day	4 3 1 3 2 2 2 1 3 4 75%	4180
September	1st to 10th	Day	1 1 1 3 2 3 3 2 3 5% 75%	2280
	11th to 20th	Day	5% 5% 2 5% 4 3 4 3 6% 5% 58%	2280
	21st to end	Day	4 6% 2 7% 3 3 2 2 4 6% 59%	2013
October	1st to 10th	Day	7% 8% 3 6% 4 3 3 3 3 5% 55%	1900
	11th to 20th	Day	8% 7% 4 7% 5% 3 4 4 6% 6% 47%	1900
	21st to end	Day	10% 10% 3 8% 4 3 4 2 6% 6% 43%	2077
November	1st to 10th	Day	10% 14% 5% 10% 5% 4 4 3 4 9% 31%	1683
	11th to 20th	Day	8% 14% 6% 10% 7% 4 6% 5% 6% 6% 27%	1539
	21st to end	Day	8% 15% 5% 12% 6% 4 4 3 5% 7% 31%	1520
December	1st to 10th	Day	8% 13% 5% 10% 6% 5% 4 3 6% 6% 33%	1520
	11th to 20th	Day	12% 19% 6% 10% 5% 4 4 4 7% 7% 22%	1928
	21st to end	Day	9% 19% 7% 13% 8% 6% 5% 3 4 5% 21%	2794
January	1st to 10th	Night	6% 20% 8% 15% 8% 6% 5% 4 5% 6% 17%	4406
	11th to 20th	Night	8% 18% 5% 17% 7% 5% 5% 3 4 4 25%	4385
	21st to end	Night	12% 19% 8% 13% 6% 5% 5% 3 4 4 21%	4521
February	1st to 10th	Night	8% 13% 5% 11% 7% 5% 4 5% 7% 5% 30%	2470
	11th to 20th	Night	6% 16% 5% 12% 7% 5% 4 3 5% 5% 32%	2402
	21st to end	Night	5% 15% 5% 14% 7% 5% 4 4 8% 6% 27%	1899
March	1st to 10th	Night	4 12% 7% 19% 9% 5% 6% 3 5% 5% 24%	3591
	11th to 20th	Night	3 13% 5% 10% 5% 3 3 3 4 5% 45%	3490
	21st to end	Night	4 15% 7% 17% 9% 7% 6% 4 5% 5% 21%	3719
April	1st to 10th	Night	8% 15% 5% 12% 7% 5% 5% 4 6% 6% 27%	1900
	11th to 20th	Night	4 13% 6% 13% 7% 5% 5% 3 5% 7% 32%	1879
	21st to end	Night	5% 11% 5% 10% 5% 5% 5% 5% 7% 8% 34%	1824
May	1st to 10th	Night	6% 10% 4 11% 4 4 3 2 4 5% 46%	2682
	11th to 20th	Night	3 5% 2 5% 3 4 3 3 4 4 64%	2516
	21st to end	Night	4 6% 3 8% 4 3 3 3 5% 6% 53%	2762
June	1st to 10th	Night	10% 9% 3 9% 4 5% 3 4 4 7% 43%	1520
	11th to 20th	Night	3 6% 2 7% 3 4 4 3 5% 6% 59%	1520
	21st to end	Night	4 3 1 3 3 3 3 2 3 5% 70%	1520
July	1st to 10th	Night	1 2 1 1 2 1 1 2 3 3 84%	2540
	11th to 20th	Night	2 2 1 3 2 2 2 2 2 4 79%	2540
	21st to end	Night	1 2 1 1 2 2 2 2 3 3 82%	2846
August	1st to 10th	Night	2 2 1 3 3 2 3 2 5% 4 72%	2848
	11th to 20th	Night	1 1 2 3 2 2 3 2 4 4 76%	2812
	21st to end	Night	5% 3 1 2 1 1 2 2 3 4 75%	3497
September	1st to 10th	Night	1 1 1 2 2 2 2 2 4 4 79%	1900
	11th to 20th	Night	4 4 1 5% 3 4 3 3 4 6% 62%	1900
	21st to end	Night	6% 6% 2 4 3 2 3 3 4 6% 61%	2163
October	1st to 10th	Night	4 7% 3 6% 4 3 3 3 4 5% 58%	2280
	11th to 20th	Night	7% 8% 3 7% 4 3 3 3 5% 5% 51%	2280
	21st to end	Night	7% 8% 4 9% 6% 4 5% 4 6% 6% 41%	2519
November	1st to 10th	Night	10% 13% 5% 11% 7% 5% 4 3 4 6% 31%	2430
	11th to 20th	Night	9% 11% 6% 12% 8% 5% 6% 5% 6% 7% 25%	2641
	21st to end	Night	6% 13% 4 10% 6% 5% 6% 4 5% 6% 34%	2660
December	1st to 10th	Night	10% 12% 5% 10% 6% 4 5% 3 6% 7% 33%	2660
	11th to 20th	Night	10% 20% 6% 12% 6% 6% 5% 3 5% 5% 22%	3276
	21st to end	Night	8% 17% 6% 13% 7% 6% 5% 4 5% 5% 27%	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	60% 9% 14% 13% 4 1	2539
	11th to 20th	Day	55% 14% 6% 13% 7% 5%	2573
	21st to end	Day	61% 8% 10% 12% 8% 2	3146
February	1st to 10th	Day	54% 7% 13% 15% 10% 2	1710
	11th to 20th	Day	55% 5% 11% 14% 11% 3	1674
	21st to end	Day	59% 5% 12% 11% 10% 3	1555
March	1st to 10th	Day	58% 4 11% 14% 11% 1	3280
	11th to 20th	Day	40% 4 12% 22% 21% 1	3490
	21st to end	Day	59% 9% 12% 14% 5%	3934
April	1st to 10th	Day	59% 6% 12% 13% 8% 2	2280
	11th to 20th	Day	53% 6% 14% 15% 10% 3	2252
	21st to end	Day	45% 7% 16% 19% 12% 1	2351
May	1st to 10th	Day	40% 5% 13% 20% 21% 1	4280
	11th to 20th	Day	25% 4 8% 24% 34% 6%	4380
	21st to end	Day	32% 7% 17% 32% 12%	4814
June	1st to 10th	Day	40% 7% 13% 25% 14% 1	2660
	11th to 20th	Day	30% 6% 13% 28% 19% 4	2660
	21st to end	Day	20% 3 9% 27% 29% 11%	2660
July	1st to 10th	Day	7% 2 5% 13% 21% 52%	4351
	11th to 20th	Day	13% 2 4 10% 24% 47%	4345
	21st to end	Day	8% 1 3 16% 42% 29%	4555
August	1st to 10th	Day	17% 3 4 16% 29% 31%	4076
	11th to 20th	Day	14% 3 5% 27% 36% 15%	4065
	21st to end	Day	16% 3 5% 27% 30% 19%	4179
September	1st to 10th	Day	13% 2 5% 21% 34% 25%	2280
	11th to 20th	Day	27% 4 8% 22% 28% 12%	2280
	21st to end	Day	28% 3 8% 22% 26% 13%	2013
October	1st to 10th	Day	33% 5% 9% 15% 25% 13%	1900
	11th to 20th	Day	36% 6% 11% 19% 21% 7%	1900
	21st to end	Day	41% 5% 11% 17% 18% 8%	2077
November	1st to 10th	Day	51% 6% 10% 14% 16% 3	1683
	11th to 20th	Day	55% 7% 13% 11% 10% 4	1539
	21st to end	Day	53% 4 10% 13% 13% 7%	1520
December	1st to 10th	Day	48% 8% 10% 18% 13% 3	1520
	11th to 20th	Day	58% 6% 14% 13% 8% 1	1928
	21st to end	Day	62% 10% 7% 13% 7% 2	2794
January	1st to 10th	Night	59% 10% 13% 11% 5% 1	4406
	11th to 20th	Night	54% 12% 7% 14% 8% 5%	4385
	21st to end	Night	64% 7% 8% 9% 9% 2	4521
February	1st to 10th	Night	53% 7% 14% 14% 11% 2	2470
	11th to 20th	Night	55% 4 11% 16% 10% 3	2404
	21st to end	Night	54% 8% 12% 15% 9% 3	1899
March	1st to 10th	Night	52% 9% 14% 15% 8% 1	3591
	11th to 20th	Night	40% 5% 12% 23% 19% 1	3490
	21st to end	Night	56% 11% 14% 12% 6%	3719
April	1st to 10th	Night	55% 6% 14% 15% 9% 1	1900
	11th to 20th	Night	50% 6% 14% 17% 9% 4	1879
	21st to end	Night	46% 8% 14% 20% 11% 1	1824
May	1st to 10th	Night	36% 6% 13% 27% 15% 3	2682
	11th to 20th	Night	25% 4 10% 25% 33% 3	2516
	21st to end	Night	28% 7% 21% 36% 8%	2762
June	1st to 10th	Night	42% 6% 12% 27% 12% 1	1520
	11th to 20th	Night	27% 6% 12% 30% 21% 4	1520
	21st to end	Night	19% 3 9% 32% 29% 9%	1520
July	1st to 10th	Night	8% 2 5% 13% 19% 54%	2500
	11th to 20th	Night	11% 2 3 12% 25% 47%	2492
	21st to end	Night	9% 2 3 15% 42% 29%	2757
August	1st to 10th	Night	16% 3 4 16% 32% 28%	2839
	11th to 20th	Night	13% 3 4 29% 35% 17%	2839
	21st to end	Night	15% 4 6% 27% 28% 21%	3497
September	1st to 10th	Night	11% 2 5% 23% 35% 24%	1900
	11th to 20th	Night	23% 4 10% 22% 29% 13%	1900
	21st to end	Night	25% 3 9% 24% 22% 17%	2163
October	1st to 10th	Night	28% 5% 10% 17% 27% 13%	2280
	11th to 20th	Night	35% 4 12% 17% 21% 10%	2280
	21st to end	Night	40% 7% 12% 14% 18% 9%	2519
November	1st to 10th	Night	54% 4 10% 13% 15% 4	2430
	11th to 20th	Night	55% 7% 11% 12% 12% 3	2641
	21st to end	Night	50% 6% 9% 12% 14% 8%	2660
December	1st to 10th	Night	48% 8% 10% 16% 16% 3	2660
	11th to 20th	Night	60% 7% 8% 12% 11% 1	3276
	21st to end	Night	56% 9% 9% 16% 9% 2	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	34% 29% 19% 9% 7% 1	180
	11th to 20th	Day	36% 14% 23% 19% 7% 3	200
	21st to end	Day	25% 23% 21% 19% 11% 2	407
February	1st to 10th	Day	27% 19% 27% 19% 7% 1	370
	11th to 20th	Day	29% 24% 23% 16% 8%	365
	21st to end	Day	29% 21% 26% 19% 5% 1	375
March	1st to 10th	Day	31% 24% 22% 20% 3	460
	11th to 20th	Day	23% 21% 25% 21% 9% 1	460
	21st to end	Day	31% 23% 25% 18% 3	506
April	1st to 10th	Day	27% 21% 26% 17% 7% 2	460
	11th to 20th	Day	31% 18% 28% 15% 6% 2	452
	21st to end	Day	21% 26% 23% 20% 8% 2	460
May	1st to 10th	Day	18% 20% 31% 21% 8% 3	463
	11th to 20th	Day	28% 15% 22% 19% 13% 3	488
	21st to end	Day	22% 14% 24% 22% 14% 4	529
June	1st to 10th	Day	17% 16% 27% 21% 17% 3	490
	11th to 20th	Day	15% 19% 30% 23% 10% 2	490
	21st to end	Day	6% 13% 28% 30% 18% 6%	490
July	1st to 10th	Day	6% 8% 34% 33% 16% 4	486
	11th to 20th	Day	2 9% 36% 31% 17% 5%	484
	21st to end	Day	2 7% 33% 33% 18% 8%	531
August	1st to 10th	Day	2 7% 29% 33% 21% 8%	487
	11th to 20th	Day	5% 9% 25% 31% 22% 8%	477
	21st to end	Day	6% 9% 28% 31% 21% 5%	539
September	1st to 10th	Day	4 8% 29% 33% 21% 4	490
	11th to 20th	Day	13% 12% 25% 32% 16% 2	490
	21st to end	Day	13% 13% 28% 28% 17% 2	490
October	1st to 10th	Day	19% 14% 25% 25% 15% 2	490
	11th to 20th	Day	19% 12% 25% 24% 18% 2	490
	21st to end	Day	24% 16% 25% 17% 14% 4	526
November	1st to 10th	Day	23% 15% 26% 20% 14% 1	273
	11th to 20th	Day	19% 14% 34% 17% 13% 3	189
	21st to end	Day	27% 18% 18% 23% 13% 2	180
December	1st to 10th	Day	26% 16% 21% 22% 11% 4	180
	11th to 20th	Day	31% 17% 24% 18% 8% 1	180
	21st to end	Day	27% 22% 22% 18% 12%	198
January	1st to 10th	Night	26% 18% 22% 19% 11% 4	760
	11th to 20th	Night	24% 16% 18% 23% 15% 3	760
	21st to end	Night	22% 14% 18% 26% 16% 4	836
February	1st to 10th	Night	22% 14% 23% 27% 13% 1	760
	11th to 20th	Night	19% 18% 21% 27% 14% 1	744
	21st to end	Night	22% 16% 24% 29% 9% 1	628
March	1st to 10th	Night	24% 19% 20% 24% 12% 2	760
	11th to 20th	Night	21% 13% 18% 29% 18% 1	760
	21st to end	Night	25% 18% 22% 24% 9% 1	836
April	1st to 10th	Night	24% 14% 23% 26% 12% 2	760
	11th to 20th	Night	17% 18% 25% 21% 16% 3	751
	21st to end	Night	15% 15% 24% 28% 17% 2	684
May	1st to 10th	Night	17% 10% 23% 29% 18% 3	470
	11th to 20th	Night	15% 10% 15% 35% 23% 3	374
	21st to end	Night	16% 7% 19% 30% 24% 4	411
June	1st to 10th	Night	19% 7% 12% 34% 27% 1	380
	11th to 20th	Night	7% 8% 21% 41% 21% 2	380
	21st to end	Night	8% 3 12% 46% 30% 2	380
July	1st to 10th	Night	3 1 10% 44% 40% 2	370
	11th to 20th	Night	3 1 8% 57% 30% 1	368
	21st to end	Night	2 1 7% 47% 38% 5%	465
August	1st to 10th	Night	2 1 7% 43% 42% 6%	567
	11th to 20th	Night	2 7% 37% 47% 7%	564
	21st to end	Night	4 2 15% 45% 31% 3	835
September	1st to 10th	Night	3 3 14% 43% 33% 4	760
	11th to 20th	Night	8% 6% 11% 34% 35% 6%	760
	21st to end	Night	13% 6% 13% 33% 28% 7%	760
October	1st to 10th	Night	10% 8% 18% 35% 26% 4	760
	11th to 20th	Night	17% 8% 14% 31% 26% 4	760
	21st to end	Night	19% 11% 19% 29% 17% 6%	836
November	1st to 10th	Night	22% 14% 19% 27% 15% 3	748
	11th to 20th	Night	25% 14% 20% 27% 13% 2	760
	21st to end	Night	20% 14% 22% 26% 15% 4	760
December	1st to 10th	Night	23% 12% 21% 26% 15% 3	760
	11th to 20th	Night	25% 16% 19% 24% 14% 2	760
	21st to end	Night	25% 22% 22% 22% 8% 2	836

Page generated at 2024-10-30 10:19:22. Version ac07

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