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 2024-03-08.

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	7% 11% 5% 7% 5% 3 4 4 4 6% 44%	78567
	Night	7% 11% 5% 9% 7% 3 5% 4 5% 6% 40%	81022
Transparency	Day	41% 5% 10% 18% 18% 8%	78273
	Night	44% 6% 10% 17% 16% 7%	80837
Seeing	Day	19% 15% 26% 24% 13% 3	13872
	Night	17% 11% 18% 30% 20% 3	23106

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% 16% 10% 16% 9% 4 5% 4 4 5% 20%	2539
	11th to 20th	Day	13% 17% 6% 12% 7% 4 5% 3 5% 4 24%	2573
	21st to end	Day	10% 23% 7% 9% 6% 3 4 4 4 6% 22%	3146
February	1st to 10th	Day	10% 15% 6% 8% 7% 3 5% 6% 6% 8% 27%	1710
	11th to 20th	Day	7% 15% 8% 12% 7% 4 4 4 4 7% 29%	1665
	21st to end	Day	7% 15% 10% 13% 7% 4 4 5% 4 5% 26%	1555
March	1st to 10th	Day	9% 18% 9% 12% 8% 3 5% 3 4 5% 24%	1951
	11th to 20th	Day	10% 18% 6% 9% 7% 2 4 4 5% 7% 28%	1980
	21st to end	Day	8% 21% 9% 12% 8% 4 4 4 4 5% 22%	2236
April	1st to 10th	Day	10% 18% 8% 11% 7% 4 4 4 4 6% 25%	2160
	11th to 20th	Day	8% 17% 7% 10% 6% 3 4 4 4 6% 30%	2129
	21st to end	Day	5% 14% 5% 9% 6% 2 4 5% 5% 7% 37%	2227
May	1st to 10th	Day	7% 9% 5% 8% 5% 3 3 5% 5% 7% 44%	2432
	11th to 20th	Day	9% 11% 4 7% 5% 4 4 5% 5% 8% 38%	2477
	21st to end	Day	10% 13% 5% 8% 6% 3 4 4 4 8% 35%	2723
June	1st to 10th	Day	10% 8% 4 5% 6% 3 4 5% 6% 8% 41%	2520
	11th to 20th	Day	4 6% 3 7% 5% 3 4 4 4 6% 53%	2520
	21st to end	Day	5% 4 2 4 3 2 3 3 3 6% 67%	2520
July	1st to 10th	Day	2 2 1 3 2 2 3 2 3 4 76%	2520
	11th to 20th	Day	3 1 2 2 2 1 3 2 3 4 77%	2520
	21st to end	Day	1 2 2 3 2 1 2 2 2 3 80%	2691
August	1st to 10th	Day	2 2 1 2 2 2 3 2 5% 5% 73%	2328
	11th to 20th	Day	3 2 1 2 2 1 2 3 3 5% 75%	2298
	21st to end	Day	2 2 1 2 2 1 2 2 3 5% 79%	2376
September	1st to 10th	Day	1 1 1 3 2 2 3 3 3 5% 75%	2160
	11th to 20th	Day	5% 5% 2 4 5% 2 4 3 5% 6% 59%	2160
	21st to end	Day	5% 7% 3 6% 4 2 3 3 4 6% 58%	1908
October	1st to 10th	Day	7% 9% 3 6% 5% 2 3 4 3 5% 53%	1800
	11th to 20th	Day	9% 7% 4 6% 6% 2 4 5% 6% 6% 47%	1800
	21st to end	Day	10% 10% 3 7% 5% 3 4 3 6% 6% 44%	1968
November	1st to 10th	Day	10% 14% 5% 10% 6% 3 4 4 4 9% 32%	1674
	11th to 20th	Day	9% 13% 6% 9% 9% 4 5% 6% 6% 5% 28%	1539
	21st to end	Day	9% 13% 6% 11% 7% 3 4 4 5% 7% 31%	1520
December	1st to 10th	Day	8% 12% 6% 9% 7% 4 4 4 6% 6% 33%	1520
	11th to 20th	Day	12% 18% 7% 9% 6% 3 4 5% 7% 7% 23%	1928
	21st to end	Day	9% 19% 7% 12% 9% 5% 5% 4 4 5% 21%	2794
January	1st to 10th	Night	6% 19% 8% 13% 10% 4 6% 5% 5% 6% 17%	4406
	11th to 20th	Night	8% 17% 5% 15% 10% 3 5% 4 4 4 25%	4385
	21st to end	Night	12% 18% 8% 12% 7% 4 5% 4 4 4 21%	4521
February	1st to 10th	Night	8% 12% 6% 10% 8% 4 4 5% 6% 6% 30%	2470
	11th to 20th	Night	7% 14% 6% 10% 9% 3 5% 4 4 5% 32%	2402
	21st to end	Night	6% 13% 6% 13% 8% 4 5% 4 7% 6% 28%	1899
March	1st to 10th	Night	7% 14% 7% 11% 10% 4 6% 5% 5% 6% 23%	2166
	11th to 20th	Night	6% 16% 7% 10% 8% 3 6% 5% 5% 8% 27%	1980
	21st to end	Night	7% 15% 7% 13% 12% 4 5% 4 5% 6% 23%	2120
April	1st to 10th	Night	9% 14% 5% 10% 9% 4 6% 5% 6% 6% 27%	1800
	11th to 20th	Night	4 12% 7% 11% 8% 4 4 5% 5% 6% 32%	1779
	21st to end	Night	5% 11% 5% 9% 6% 3 6% 6% 7% 8% 36%	1728
May	1st to 10th	Night	6% 10% 3 6% 5% 3 4 3 5% 7% 47%	1526
	11th to 20th	Night	5% 9% 4 8% 7% 4 7% 6% 6% 7% 38%	1416
	21st to end	Night	8% 10% 4 9% 6% 3 4 4 5% 9% 39%	1552
June	1st to 10th	Night	10% 8% 3 8% 5% 4 4 5% 4 8% 42%	1440
	11th to 20th	Night	3 5% 2 5% 4 3 5% 3 4 6% 58%	1440
	21st to end	Night	4 3 1 3 3 2 3 3 3 5% 70%	1440
July	1st to 10th	Night	1 3 1 2 3 2 2 4 5% 5% 73%	1440
	11th to 20th	Night	2 2 1 3 3 1 2 2 2 4 78%	1440
	21st to end	Night	1 2 1 1 2 1 2 2 3 4 82%	1622
August	1st to 10th	Night	1 1 1 2 3 2 3 4 5% 5% 72%	1611
	11th to 20th	Night	1 1 2 2 3 2 2 2 4 4 76%	1602
	21st to end	Night	1 3 1 2 2 1 2 2 3 5% 78%	1979
September	1st to 10th	Night	1 1 1 2 2 1 2 2 3 4 79%	1800
	11th to 20th	Night	4 3 2 4 4 3 3 4 4 6% 64%	1800
	21st to end	Night	6% 6% 2 4 4 2 3 3 4 6% 59%	2048
October	1st to 10th	Night	4 7% 3 6% 4 2 3 4 5% 5% 57%	2160
	11th to 20th	Night	7% 7% 4 6% 5% 2 4 3 5% 5% 51%	2160
	21st to end	Night	7% 8% 4 8% 7% 3 4 5% 6% 6% 42%	2386
November	1st to 10th	Night	11% 12% 6% 10% 8% 5% 4 4 4 6% 32%	2405
	11th to 20th	Night	9% 11% 6% 10% 9% 5% 6% 6% 6% 7% 26%	2641
	21st to end	Night	6% 12% 6% 8% 7% 4 6% 5% 5% 6% 34%	2660
December	1st to 10th	Night	10% 11% 6% 9% 7% 3 4 5% 5% 7% 33%	2660
	11th to 20th	Night	10% 20% 6% 10% 8% 4 6% 4 5% 5% 22%	3276
	21st to end	Night	8% 16% 6% 11% 8% 4 6% 5% 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	62% 5% 11% 13% 8% 1	1951
	11th to 20th	Day	55% 6% 11% 18% 9% 2	1980
	21st to end	Day	64% 6% 11% 12% 6% 1	2236
April	1st to 10th	Day	61% 6% 11% 12% 8% 3	2160
	11th to 20th	Day	55% 5% 14% 14% 10% 3	2132
	21st to end	Day	45% 7% 16% 19% 12% 1	2227
May	1st to 10th	Day	40% 4 13% 27% 15% 1	2432
	11th to 20th	Day	44% 6% 12% 24% 12% 2	2480
	21st to end	Day	48% 6% 15% 21% 10% 1	2724
June	1st to 10th	Day	41% 7% 13% 25% 13% 1	2520
	11th to 20th	Day	31% 6% 14% 29% 18% 3	2520
	21st to end	Day	20% 4 10% 27% 29% 11%	2520
July	1st to 10th	Day	13% 3 9% 23% 29% 23%	2451
	11th to 20th	Day	12% 3 6% 17% 33% 29%	2445
	21st to end	Day	11% 2 4 14% 42% 27%	2541
August	1st to 10th	Day	14% 3 7% 27% 29% 19%	2312
	11th to 20th	Day	14% 2 6% 22% 39% 17%	2298
	21st to end	Day	11% 1 6% 23% 42% 17%	2376
September	1st to 10th	Day	13% 2 5% 21% 34% 26%	2160
	11th to 20th	Day	26% 3 8% 22% 29% 13%	2160
	21st to end	Day	29% 3 8% 22% 25% 14%	1908
October	1st to 10th	Day	34% 5% 9% 15% 25% 12%	1800
	11th to 20th	Day	36% 5% 10% 19% 21% 8%	1800
	21st to end	Day	40% 5% 11% 17% 17% 9%	1968
November	1st to 10th	Day	51% 6% 11% 14% 16% 3	1674
	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	58% 7% 10% 13% 10% 1	2166
	11th to 20th	Night	56% 6% 11% 14% 13% 1	1980
	21st to end	Night	61% 6% 12% 13% 7%	2120
April	1st to 10th	Night	57% 6% 13% 15% 9% 1	1800
	11th to 20th	Night	52% 6% 14% 16% 10% 4	1779
	21st to end	Night	46% 7% 14% 20% 12% 1	1728
May	1st to 10th	Night	35% 6% 13% 30% 14% 2	1526
	11th to 20th	Night	45% 7% 13% 23% 11% 2	1416
	21st to end	Night	43% 8% 16% 23% 10% 1	1552
June	1st to 10th	Night	42% 6% 12% 27% 11% 1	1440
	11th to 20th	Night	28% 6% 12% 31% 20% 3	1440
	21st to end	Night	20% 4 9% 31% 28% 8%	1440
July	1st to 10th	Night	14% 3 9% 23% 28% 23%	1400
	11th to 20th	Night	12% 2 4 21% 33% 28%	1392
	21st to end	Night	9% 2 3 14% 45% 27%	1532
August	1st to 10th	Night	13% 5% 7% 27% 32% 15%	1602
	11th to 20th	Night	13% 2 6% 25% 38% 15%	1602
	21st to end	Night	12% 2 7% 23% 37% 19%	1979
September	1st to 10th	Night	11% 2 5% 24% 35% 24%	1800
	11th to 20th	Night	22% 3 10% 21% 30% 14%	1800
	21st to end	Night	27% 3 8% 24% 21% 17%	2048
October	1st to 10th	Night	29% 5% 11% 16% 27% 12%	2160
	11th to 20th	Night	35% 4 11% 17% 21% 11%	2160
	21st to end	Night	40% 7% 12% 14% 18% 9%	2386
November	1st to 10th	Night	54% 4 10% 13% 15% 4	2405
	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	449
	11th to 20th	Day	24% 20% 26% 22% 7% 1	420
	21st to end	Day	30% 22% 26% 18% 3	462
April	1st to 10th	Day	29% 21% 25% 16% 6% 2	420
	11th to 20th	Day	32% 18% 28% 14% 6% 2	412
	21st to end	Day	22% 25% 23% 20% 8% 2	420
May	1st to 10th	Day	16% 20% 31% 22% 8% 3	423
	11th to 20th	Day	30% 16% 21% 18% 11% 2	448
	21st to end	Day	23% 13% 24% 22% 13% 5%	485
June	1st to 10th	Day	17% 16% 26% 20% 17% 3	450
	11th to 20th	Day	15% 19% 30% 24% 10% 2	450
	21st to end	Day	6% 11% 27% 31% 19% 6%	450
July	1st to 10th	Day	6% 8% 34% 33% 16% 4	446
	11th to 20th	Day	3 8% 35% 32% 17% 5%	444
	21st to end	Day	2 6% 32% 34% 18% 8%	487
August	1st to 10th	Day	2 6% 29% 34% 21% 9%	447
	11th to 20th	Day	5% 7% 24% 33% 23% 9%	437
	21st to end	Day	6% 7% 29% 31% 21% 5%	495
September	1st to 10th	Day	4 8% 29% 32% 22% 4	450
	11th to 20th	Day	12% 12% 24% 33% 17% 3	450
	21st to end	Day	13% 14% 27% 27% 17% 2	450
October	1st to 10th	Day	20% 14% 24% 24% 16% 2	450
	11th to 20th	Day	19% 13% 24% 24% 18% 2	450
	21st to end	Day	24% 16% 24% 18% 15% 4	483
November	1st to 10th	Day	22% 16% 26% 20% 14% 1	270
	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% 11% 2	750
	11th to 20th	Night	22% 13% 17% 30% 17% 1	720
	21st to end	Night	26% 17% 22% 25% 9% 1	792
April	1st to 10th	Night	25% 13% 22% 25% 13% 2	720
	11th to 20th	Night	17% 18% 23% 21% 17% 4	711
	21st to end	Night	15% 15% 23% 28% 17% 2	648
May	1st to 10th	Night	16% 9% 22% 30% 19% 3	446
	11th to 20th	Night	16% 10% 15% 33% 24% 3	354
	21st to end	Night	16% 7% 19% 30% 24% 4	389
June	1st to 10th	Night	19% 7% 12% 33% 28% 1	360
	11th to 20th	Night	6% 8% 21% 40% 22% 3	360
	21st to end	Night	8% 2 11% 46% 31% 2	360
July	1st to 10th	Night	3 1 9% 44% 41% 2	350
	11th to 20th	Night	3 1 8% 57% 30% 1	348
	21st to end	Night	2 1 6% 48% 39% 5%	440
August	1st to 10th	Night	2 1 7% 42% 43% 6%	537
	11th to 20th	Night	2 6% 36% 48% 7%	534
	21st to end	Night	4 2 15% 45% 32% 3	791
September	1st to 10th	Night	3 3 13% 42% 33% 5%	720
	11th to 20th	Night	7% 6% 10% 34% 37% 6%	720
	21st to end	Night	13% 6% 13% 33% 28% 7%	720
October	1st to 10th	Night	10% 8% 18% 34% 25% 4	720
	11th to 20th	Night	16% 8% 14% 31% 26% 5%	720
	21st to end	Night	19% 10% 18% 29% 18% 6%	792
November	1st to 10th	Night	21% 14% 20% 27% 15% 3	740
	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 2024-03-05 04:24:02. Version ac07

Copyright © 2024 Attilla Danko.