Cascade
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Cascade clear sky chart from 2005-11-06 to 2024-11-03.

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% 10% 3 7% 4 4 4 3 5% 6% 47%	101343
	Night	7% 11% 4 7% 4 4 4 3 5% 6% 46%	97813
Transparency	Day	37% 6% 10% 19% 17% 11%	101087
	Night	38% 7% 11% 20% 16% 8%	97658
Seeing	Day	13% 17% 31% 25% 11% 2	14381
	Night	14% 7% 21% 36% 20% 3	23650

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	5% 18% 9% 15% 5% 6% 5% 3 5% 6% 23%	2539
	11th to 20th	Day	8% 20% 7% 14% 4 4 3 3 3 4 28%	2540
	21st to end	Day	12% 21% 6% 8% 5% 5% 3 3 4 7% 26%	2794
February	1st to 10th	Day	8% 21% 6% 12% 6% 4 3 3 4 5% 28%	1621
	11th to 20th	Day	8% 20% 7% 11% 5% 4 4 4 4 5% 27%	1850
	21st to end	Day	8% 22% 8% 16% 6% 3 3 3 5% 5% 22%	1570
March	1st to 10th	Day	6% 18% 8% 14% 6% 4 5% 3 5% 6% 25%	3138
	11th to 20th	Day	7% 14% 3 7% 4 4 3 3 3 4 49%	3361
	21st to end	Day	8% 18% 5% 12% 8% 8% 6% 4 5% 6% 19%	3996
April	1st to 10th	Day	10% 19% 3 9% 6% 5% 5% 4 5% 6% 27%	2280
	11th to 20th	Day	8% 14% 3 9% 7% 4 4 3 5% 6% 36%	2313
	21st to end	Day	10% 15% 3 7% 5% 5% 5% 4 5% 6% 36%	2470
May	1st to 10th	Day	6% 13% 5% 9% 5% 5% 5% 3 4 5% 39%	4110
	11th to 20th	Day	6% 5% 1 5% 4 4 4 4 5% 7% 54%	4248
	21st to end	Day	7% 11% 3 7% 5% 4 5% 4 5% 7% 41%	4813
June	1st to 10th	Day	12% 7% 3 8% 7% 6% 6% 5% 6% 7% 33%	2660
	11th to 20th	Day	12% 7% 3 6% 5% 4 4 4 5% 7% 45%	2660
	21st to end	Day	4 4 2 5% 3 3 3 3 4 5% 64%	2660
July	1st to 10th	Day	1 1 2 2 2 2 2 4 4 79%	4420
	11th to 20th	Day	2 2 1 2 2 2 2 2 3 4 76%	4420
	21st to end	Day	2 2 1 3 2 3 3 3 4 5% 73%	4790
August	1st to 10th	Day	3 3 1 5% 3 5% 5% 4 6% 7% 59%	4260
	11th to 20th	Day	2 1 3 2 3 3 3 4 6% 74%	4028
	21st to end	Day	3 3 1 3 2 3 3 3 3 5% 71%	4253
September	1st to 10th	Day	4 3 1 3 2 3 3 3 5% 6% 70%	2280
	11th to 20th	Day	7% 4 2 4 4 4 4 3 5% 7% 56%	2104
	21st to end	Day	7% 4 1 4 2 4 4 3 4 6% 60%	2090
October	1st to 10th	Day	10% 8% 2 5% 5% 4 4 3 4 5% 50%	2090
	11th to 20th	Day	9% 9% 2 6% 4 4 4 3 3 6% 50%	1815
	21st to end	Day	9% 11% 3 8% 5% 5% 5% 3 5% 6% 40%	1881
November	1st to 10th	Day	14% 14% 5% 8% 4 4 4 2 4 7% 33%	1692
	11th to 20th	Day	13% 15% 5% 7% 5% 4 4 3 6% 5% 34%	1710
	21st to end	Day	9% 15% 5% 8% 5% 4 5% 4 5% 6% 35%	1645
December	1st to 10th	Day	11% 19% 3 11% 4 3 3 2 5% 7% 32%	1520
	11th to 20th	Day	10% 20% 6% 11% 7% 4 3 2 6% 6% 24%	1928
	21st to end	Day	9% 14% 5% 11% 4 4 4 3 4 7% 34%	2794
January	1st to 10th	Night	7% 18% 8% 13% 6% 5% 5% 3 5% 5% 27%	4406
	11th to 20th	Night	9% 19% 7% 14% 5% 3 3 3 4 5% 27%	4420
	21st to end	Night	10% 25% 5% 9% 4 4 3 3 4 5% 28%	4862
February	1st to 10th	Night	9% 18% 6% 9% 6% 4 4 3 5% 5% 29%	2554
	11th to 20th	Night	8% 17% 5% 10% 5% 4 3 3 6% 5% 33%	2218
	21st to end	Night	8% 19% 8% 13% 5% 4 4 3 5% 5% 27%	1884
March	1st to 10th	Night	6% 21% 6% 10% 5% 4 3 2 4 6% 34%	3736
	11th to 20th	Night	7% 14% 4 6% 3 3 3 3 4 4 49%	3618
	21st to end	Night	7% 13% 4 9% 6% 5% 6% 5% 7% 8% 30%	3655
April	1st to 10th	Night	9% 12% 3 8% 4 5% 4 3 5% 6% 39%	1900
	11th to 20th	Night	10% 10% 4 7% 4 4 4 3 5% 6% 43%	1813
	21st to end	Night	7% 8% 3 7% 5% 4 4 4 6% 6% 48%	1710
May	1st to 10th	Night	9% 10% 2 5% 3 4 5% 4 5% 7% 46%	2860
	11th to 20th	Night	3 4 2 5% 3 4 3 3 5% 8% 59%	2644
	21st to end	Night	8% 9% 3 7% 4 4 4 2 5% 7% 49%	2762
June	1st to 10th	Night	12% 6% 2 4 4 4 5% 5% 6% 9% 43%	1520
	11th to 20th	Night	10% 4 1 4 3 3 3 3 5% 7% 55%	1520
	21st to end	Night	4 3 2 3 4 3 4 3 5% 5% 64%	1520
July	1st to 10th	Night	1 1 1 1 1 2 2 3 4 5% 80%	2540
	11th to 20th	Night	1 1 1 1 1 2 2 3 4 5% 79%	2540
	21st to end	Night	2 2 1 2 2 2 3 3 5% 6% 71%	2761
August	1st to 10th	Night	3 4 2 4 3 3 4 4 5% 7% 61%	2674
	11th to 20th	Night	1 1 1 2 2 2 3 2 4 5% 77%	2811
	21st to end	Night	4 2 1 3 2 2 2 2 4 4 73%	3420
September	1st to 10th	Night	3 3 1 3 2 3 3 3 4 5% 72%	1900
	11th to 20th	Night	5% 5% 1 5% 3 3 4 3 5% 6% 60%	2076
	21st to end	Night	8% 3 1 3 2 3 2 3 3 5% 65%	2090
October	1st to 10th	Night	8% 5% 1 4 3 4 4 3 6% 8% 54%	2090
	11th to 20th	Night	9% 6% 2 5% 4 3 3 3 5% 7% 52%	2362
	21st to end	Night	9% 9% 2 6% 4 4 5% 4 6% 7% 44%	2717
November	1st to 10th	Night	13% 11% 3 8% 5% 4 4 3 5% 7% 37%	2431
	11th to 20th	Night	14% 13% 3 6% 5% 4 4 3 5% 7% 36%	2470
	21st to end	Night	9% 13% 3 8% 6% 5% 3 3 4 6% 40%	2531
December	1st to 10th	Night	11% 15% 5% 9% 5% 4 4 4 5% 6% 33%	2660
	11th to 20th	Night	11% 18% 5% 10% 5% 6% 4 4 5% 5% 27%	3276
	21st to end	Night	8% 15% 5% 10% 5% 4 4 3 5% 6% 34%	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% 11% 13% 14% 2 1	2539
	11th to 20th	Day	60% 7% 9% 15% 8% 1	2540
	21st to end	Day	59% 8% 16% 13% 3 1	2794
February	1st to 10th	Day	60% 7% 12% 16% 4 1	1621
	11th to 20th	Day	60% 8% 11% 15% 6%	1860
	21st to end	Day	63% 7% 10% 13% 6% 1	1570
March	1st to 10th	Day	57% 8% 8% 13% 13%	3138
	11th to 20th	Day	40% 6% 8% 36% 10%	3361
	21st to end	Day	60% 13% 11% 12% 4 1	3996
April	1st to 10th	Day	56% 8% 14% 16% 6% 1	2280
	11th to 20th	Day	47% 7% 12% 20% 12% 2	2316
	21st to end	Day	47% 8% 13% 21% 10%	2470
May	1st to 10th	Day	44% 8% 10% 22% 15% 1	4110
	11th to 20th	Day	26% 6% 10% 33% 19% 6%	4251
	21st to end	Day	38% 9% 13% 28% 10% 1	4814
June	1st to 10th	Day	45% 10% 12% 21% 11% 1	2660
	11th to 20th	Day	37% 6% 10% 22% 19% 6%	2660
	21st to end	Day	22% 4 8% 21% 34% 11%	2660
July	1st to 10th	Day	10% 3 4 10% 22% 51%	4351
	11th to 20th	Day	11% 3 4 8% 22% 52%	4345
	21st to end	Day	11% 3 5% 10% 31% 39%	4639
August	1st to 10th	Day	22% 5% 7% 13% 27% 27%	4244
	11th to 20th	Day	11% 4 5% 17% 42% 22%	4067
	21st to end	Day	16% 3 6% 22% 35% 18%	4252
September	1st to 10th	Day	16% 4 7% 19% 32% 22%	2280
	11th to 20th	Day	27% 5% 10% 21% 26% 11%	2104
	21st to end	Day	25% 4 9% 28% 26% 7%	2090
October	1st to 10th	Day	36% 5% 10% 23% 21% 4	2090
	11th to 20th	Day	36% 5% 11% 27% 19% 2	1815
	21st to end	Day	44% 9% 11% 21% 15% 1	1881
November	1st to 10th	Day	52% 6% 12% 20% 9% 1	1692
	11th to 20th	Day	53% 6% 15% 18% 8% 1	1710
	21st to end	Day	50% 7% 13% 16% 12% 2	1645
December	1st to 10th	Day	53% 8% 16% 14% 7% 2	1520
	11th to 20th	Day	60% 10% 12% 12% 6%	1928
	21st to end	Day	50% 6% 15% 19% 9% 1	2794
January	1st to 10th	Night	57% 9% 13% 17% 3 1	4406
	11th to 20th	Night	59% 7% 9% 15% 8% 1	4420
	21st to end	Night	58% 8% 12% 15% 5% 1	4862
February	1st to 10th	Night	56% 8% 13% 16% 5% 1	2554
	11th to 20th	Night	53% 8% 13% 16% 9% 1	2219
	21st to end	Night	60% 6% 10% 15% 7% 2	1884
March	1st to 10th	Night	50% 8% 10% 16% 15% 1	3736
	11th to 20th	Night	39% 6% 8% 33% 13% 1	3618
	21st to end	Night	45% 15% 18% 18% 5%	3655
April	1st to 10th	Night	44% 8% 14% 23% 10% 1	1900
	11th to 20th	Night	41% 6% 14% 22% 14% 3	1813
	21st to end	Night	36% 8% 16% 26% 14%	1710
May	1st to 10th	Night	33% 9% 10% 28% 18% 1	2860
	11th to 20th	Night	21% 6% 12% 34% 25% 1	2644
	21st to end	Night	35% 7% 13% 34% 10% 1	2762
June	1st to 10th	Night	36% 9% 17% 28% 10%	1520
	11th to 20th	Night	29% 5% 12% 29% 20% 6%	1520
	21st to end	Night	21% 4 8% 24% 31% 12%	1520
July	1st to 10th	Night	8% 3 4 12% 25% 48%	2500
	11th to 20th	Night	7% 3 5% 12% 20% 54%	2492
	21st to end	Night	12% 4 4 12% 31% 37%	2674
August	1st to 10th	Night	20% 5% 6% 13% 36% 21%	2666
	11th to 20th	Night	10% 3 5% 16% 40% 26%	2838
	21st to end	Night	15% 3 5% 20% 33% 23%	3420
September	1st to 10th	Night	16% 3 6% 21% 31% 22%	1900
	11th to 20th	Night	24% 5% 9% 21% 26% 15%	2076
	21st to end	Night	22% 4 8% 29% 26% 11%	2090
October	1st to 10th	Night	27% 7% 11% 25% 24% 6%	2090
	11th to 20th	Night	32% 5% 13% 27% 20% 3	2362
	21st to end	Night	38% 7% 14% 22% 17% 2	2717
November	1st to 10th	Night	47% 6% 12% 21% 11% 2	2431
	11th to 20th	Night	48% 8% 13% 22% 9%	2470
	21st to end	Night	47% 6% 11% 20% 13% 3	2531
December	1st to 10th	Night	51% 8% 14% 15% 9% 2	2660
	11th to 20th	Night	59% 8% 11% 16% 5% 1	3276
	21st to end	Night	49% 8% 15% 17% 9% 3	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% 15% 30% 24% 11% 3	180
	11th to 20th	Day	21% 16% 25% 21% 11% 7%	180
	21st to end	Day	17% 15% 33% 21% 10% 5%	198
February	1st to 10th	Day	21% 21% 33% 15% 8% 2	239
	11th to 20th	Day	20% 20% 35% 16% 8%	455
	21st to end	Day	22% 23% 30% 18% 7%	382
March	1st to 10th	Day	22% 24% 34% 17% 2	460
	11th to 20th	Day	19% 18% 31% 21% 9% 1	460
	21st to end	Day	20% 24% 32% 17% 6% 1	506
April	1st to 10th	Day	21% 24% 28% 18% 8% 2	460
	11th to 20th	Day	20% 29% 26% 18% 6% 1	452
	21st to end	Day	17% 23% 31% 19% 8% 2	460
May	1st to 10th	Day	11% 22% 33% 24% 9% 1	463
	11th to 20th	Day	19% 17% 29% 24% 9% 2	488
	21st to end	Day	14% 16% 26% 28% 13% 3	529
June	1st to 10th	Day	14% 19% 26% 24% 13% 3	490
	11th to 20th	Day	16% 22% 32% 18% 10% 1	490
	21st to end	Day	4 14% 34% 32% 13% 3	490
July	1st to 10th	Day	3 11% 40% 33% 11% 2	486
	11th to 20th	Day	3 14% 38% 31% 12% 2	484
	21st to end	Day	3 8% 39% 33% 15% 1	531
August	1st to 10th	Day	5% 10% 37% 32% 13% 3	487
	11th to 20th	Day	2 9% 31% 37% 17% 3	477
	21st to end	Day	6% 12% 32% 32% 17% 3	539
September	1st to 10th	Day	6% 10% 30% 34% 17% 3	490
	11th to 20th	Day	9% 12% 31% 31% 15% 1	490
	21st to end	Day	8% 14% 31% 31% 15% 1	490
October	1st to 10th	Day	14% 14% 27% 29% 15% 1	490
	11th to 20th	Day	15% 14% 25% 23% 17% 5%	362
	21st to end	Day	18% 18% 26% 25% 9% 3	330
November	1st to 10th	Day	24% 13% 25% 25% 12% 1	276
	11th to 20th	Day	14% 19% 25% 26% 12% 3	270
	21st to end	Day	15% 12% 28% 29% 13% 3	239
December	1st to 10th	Day	23% 13% 22% 22% 14% 6%	180
	11th to 20th	Day	26% 17% 28% 19% 9% 2	180
	21st to end	Day	20% 17% 28% 23% 9% 3	198
January	1st to 10th	Night	22% 9% 22% 29% 17% 2	760
	11th to 20th	Night	23% 8% 21% 27% 18% 3	760
	21st to end	Night	17% 9% 24% 28% 20% 3	836
February	1st to 10th	Night	20% 9% 28% 30% 10% 2	760
	11th to 20th	Night	19% 10% 26% 30% 14% 2	744
	21st to end	Night	18% 11% 25% 33% 11% 2	628
March	1st to 10th	Night	20% 12% 25% 29% 12% 2	760
	11th to 20th	Night	17% 9% 23% 33% 17% 1	760
	21st to end	Night	17% 11% 26% 34% 10% 1	836
April	1st to 10th	Night	15% 11% 22% 32% 17% 3	760
	11th to 20th	Night	14% 13% 29% 29% 14% 2	685
	21st to end	Night	11% 9% 25% 39% 14% 2	570
May	1st to 10th	Night	9% 8% 25% 36% 20% 1	570
	11th to 20th	Night	9% 6% 23% 34% 24% 4	450
	21st to end	Night	12% 4 19% 38% 24% 2	411
June	1st to 10th	Night	14% 5% 14% 40% 25% 2	380
	11th to 20th	Night	14% 1 20% 42% 21% 2	380
	21st to end	Night	4 2 13% 49% 31% 1	380
July	1st to 10th	Night	1 2 10% 54% 31% 2	370
	11th to 20th	Night	2 1 14% 59% 23% 1	368
	21st to end	Night	3 11% 55% 30% 1	416
August	1st to 10th	Night	5% 2 10% 48% 32% 3	458
	11th to 20th	Night	1 1 12% 47% 35% 3	564
	21st to end	Night	4 2 13% 43% 33% 5%	784
September	1st to 10th	Night	4 2 13% 47% 32% 3	760
	11th to 20th	Night	7% 3 13% 39% 32% 6%	760
	21st to end	Night	10% 4 16% 37% 27% 7%	760
October	1st to 10th	Night	10% 4 17% 42% 24% 2	760
	11th to 20th	Night	12% 7% 16% 38% 23% 5%	760
	21st to end	Night	15% 6% 22% 37% 17% 3	836
November	1st to 10th	Night	20% 7% 20% 35% 16% 2	748
	11th to 20th	Night	22% 8% 23% 31% 14% 2	760
	21st to end	Night	16% 8% 26% 29% 18% 4	760
December	1st to 10th	Night	18% 8% 24% 32% 16% 2	760
	11th to 20th	Night	22% 11% 22% 29% 14% 2	760
	21st to end	Night	23% 12% 25% 27% 12% 1	836

Page generated at 2024-10-31 01:39:24. Version ac07

Copyright © 2024 Attilla Danko.