Clearwater Lake
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Clearwater Lake clear sky chart from 2005-11-06 to 2024-06-17.

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	12% 10% 4 9% 6% 5% 5% 4 6% 7% 33%	89117
	Night	10% 11% 4 10% 7% 5% 5% 4 6% 6% 31%	89774
Transparency	Day	48% 8% 15% 20% 8%	88808
	Night	51% 8% 14% 19% 8%	89664
Seeing	Day	15% 10% 29% 28% 15% 4	15532
	Night	16% 7% 29% 32% 14% 2	25041

By Month

Percentage Cloud Cover NW (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% 14% 8% 21% 10% 7% 5% 5% 7% 4 12%	1899
	11th to 20th	Day	4 10% 5% 25% 12% 9% 7% 4 6% 4 13%	2076
	21st to end	Day	8% 18% 7% 13% 5% 6% 7% 5% 7% 7% 18%	2742
February	1st to 10th	Day	7% 10% 4 14% 6% 7% 8% 7% 7% 8% 22%	1520
	11th to 20th	Day	6% 11% 4 9% 7% 6% 7% 6% 9% 7% 28%	1516
	21st to end	Day	4 9% 4 13% 9% 8% 8% 5% 7% 7% 28%	1567
March	1st to 10th	Day	8% 10% 4 9% 7% 6% 6% 4 6% 9% 32%	3130
	11th to 20th	Day	7% 10% 5% 13% 7% 4 5% 4 5% 6% 34%	3317
	21st to end	Day	5% 9% 4 6% 4 4 4 4 5% 7% 50%	4037
April	1st to 10th	Day	8% 10% 3 7% 6% 6% 5% 5% 6% 6% 40%	2303
	11th to 20th	Day	11% 10% 4 9% 6% 5% 4 3 4 6% 37%	2442
	21st to end	Day	9% 7% 3 7% 5% 5% 6% 5% 6% 8% 39%	2558
May	1st to 10th	Day	15% 10% 3 8% 5% 5% 4 4 6% 7% 32%	4553
	11th to 20th	Day	18% 9% 3 6% 4 4 4 4 5% 6% 37%	4705
	21st to end	Day	19% 12% 4 7% 4 4 4 3 6% 6% 31%	5173
June	1st to 10th	Day	17% 10% 3 7% 5% 5% 5% 4 6% 7% 33%	3014
	11th to 20th	Day	18% 8% 3 7% 5% 5% 5% 5% 5% 8% 30%	2981
	21st to end	Day	15% 7% 3 7% 4 5% 6% 5% 6% 7% 35%	2880
July	1st to 10th	Day	11% 6% 2 5% 5% 4 6% 4 6% 8% 43%	2880
	11th to 20th	Day	13% 5% 2 6% 4 4 5% 5% 7% 9% 41%	2833
	21st to end	Day	12% 6% 2 6% 4 4 5% 4 6% 9% 42%	2924
August	1st to 10th	Day	10% 5% 2 5% 4 4 4 4 6% 9% 46%	2507
	11th to 20th	Day	13% 4 2 5% 4 4 5% 4 7% 10% 40%	2469
	21st to end	Day	17% 6% 2 6% 4 3 4 3 6% 8% 39%	2574
September	1st to 10th	Day	15% 6% 3 7% 5% 6% 5% 3 5% 9% 37%	2206
	11th to 20th	Day	17% 8% 3 6% 4 5% 5% 5% 6% 8% 34%	2046
	21st to end	Day	13% 9% 3 6% 5% 5% 4 3 4 9% 38%	1980
October	1st to 10th	Day	18% 15% 3 7% 5% 5% 4 4 5% 7% 28%	1853
	11th to 20th	Day	15% 19% 5% 11% 5% 5% 4 3 4 6% 23%	1620
	21st to end	Day	19% 19% 6% 13% 5% 5% 3 4 4 4 18%	1782
November	1st to 10th	Day	15% 21% 7% 13% 8% 6% 3 3 4 5% 15%	1464
	11th to 20th	Day	14% 13% 6% 16% 10% 5% 4 4 4 4 19%	1330
	21st to end	Day	8% 16% 8% 14% 9% 7% 5% 5% 5% 5% 17%	1330
December	1st to 10th	Day	5% 13% 5% 16% 11% 9% 8% 5% 7% 5% 16%	1330
	11th to 20th	Day	11% 16% 6% 12% 9% 6% 5% 4 4 6% 21%	1486
	21st to end	Day	6% 8% 3 11% 8% 7% 6% 4 6% 7% 36%	2090
January	1st to 10th	Night	5% 13% 6% 16% 11% 8% 7% 6% 6% 6% 17%	5046
	11th to 20th	Night	5% 11% 6% 25% 11% 7% 7% 5% 7% 5% 12%	4825
	21st to end	Night	9% 17% 6% 13% 7% 6% 6% 5% 6% 5% 21%	4923
February	1st to 10th	Night	7% 11% 4 11% 7% 8% 8% 5% 7% 6% 25%	2660
	11th to 20th	Night	5% 9% 5% 11% 9% 7% 6% 6% 6% 6% 29%	2550
	21st to end	Night	5% 9% 4 10% 8% 6% 5% 4 6% 8% 34%	1903
March	1st to 10th	Night	8% 13% 4 9% 5% 4 5% 3 5% 7% 39%	3734
	11th to 20th	Night	7% 9% 4 12% 7% 5% 5% 3 6% 7% 35%	3645
	21st to end	Night	5% 8% 3 5% 4 4 4 3 5% 6% 53%	3586
April	1st to 10th	Night	10% 10% 2 7% 5% 4 4 4 6% 7% 41%	1876
	11th to 20th	Night	12% 11% 3 7% 5% 5% 5% 3 6% 6% 38%	1689
	21st to end	Night	9% 9% 4 7% 5% 5% 4 4 5% 5% 43%	1620
May	1st to 10th	Night	16% 9% 3 7% 5% 4 5% 3 6% 7% 35%	2417
	11th to 20th	Night	18% 8% 3 7% 5% 4 4 4 6% 7% 33%	2201
	21st to end	Night	19% 11% 3 8% 5% 3 4 4 4 5% 35%	2414
June	1st to 10th	Night	16% 8% 2 5% 4 4 6% 4 5% 7% 39%	1163
	11th to 20th	Night	16% 8% 2 7% 6% 5% 3 5% 6% 9% 34%	1122
	21st to end	Night	15% 6% 2 6% 4 4 5% 5% 6% 7% 38%	1080
July	1st to 10th	Night	10% 5% 2 5% 5% 4 4 3 7% 8% 48%	1080
	11th to 20th	Night	9% 6% 2 4 5% 5% 6% 4 6% 9% 44%	1124
	21st to end	Night	11% 5% 2 5% 4 4 5% 4 7% 9% 44%	1391
August	1st to 10th	Night	9% 4 1 4 3 3 4 3 5% 10% 53%	1432
	11th to 20th	Night	13% 5% 2 4 4 3 4 3 6% 9% 47%	1432
	21st to end	Night	17% 6% 2 5% 3 3 3 4 6% 8% 43%	1782
September	1st to 10th	Night	13% 5% 2 5% 3 5% 4 4 6% 9% 42%	1751
	11th to 20th	Night	16% 9% 2 7% 5% 4 4 4 5% 6% 38%	1914
	21st to end	Night	15% 6% 2 6% 4 5% 5% 4 5% 7% 41%	1980
October	1st to 10th	Night	18% 12% 3 7% 4 3 4 3 5% 5% 35%	2087
	11th to 20th	Night	14% 17% 4 8% 5% 4 4 3 5% 5% 32%	2340
	21st to end	Night	20% 17% 6% 10% 5% 5% 3 3 4 5% 21%	2574
November	1st to 10th	Night	16% 20% 6% 13% 8% 6% 4 3 4 4 16%	2613
	11th to 20th	Night	12% 15% 5% 14% 11% 7% 4 3 4 6% 18%	2850
	21st to end	Night	9% 18% 6% 14% 9% 7% 5% 4 5% 5% 19%	2850
December	1st to 10th	Night	7% 14% 6% 14% 10% 9% 7% 5% 6% 5% 16%	2850
	11th to 20th	Night	8% 15% 6% 13% 8% 6% 5% 5% 6% 6% 23%	3704
	21st to end	Night	7% 11% 3 9% 8% 6% 5% 4 6% 6% 36%	5566

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	70% 9% 10% 9% 2	1899
	11th to 20th	Day	72% 6% 8% 12% 2	2097
	21st to end	Day	61% 10% 14% 11% 3	2742
February	1st to 10th	Day	56% 7% 14% 16% 7% 1	1520
	11th to 20th	Day	51% 8% 14% 18% 9%	1524
	21st to end	Day	53% 8% 13% 18% 8%	1567
March	1st to 10th	Day	47% 8% 16% 21% 7% 1	3130
	11th to 20th	Day	48% 8% 16% 17% 11%	3319
	21st to end	Day	33% 7% 13% 26% 20% 1	4037
April	1st to 10th	Day	42% 7% 15% 21% 14% 1	2303
	11th to 20th	Day	48% 6% 11% 19% 15% 1	2442
	21st to end	Day	41% 8% 14% 24% 13%	2558
May	1st to 10th	Day	47% 9% 12% 25% 7% 1	4553
	11th to 20th	Day	45% 7% 14% 22% 10% 2	4709
	21st to end	Day	51% 9% 12% 21% 8%	5173
June	1st to 10th	Day	48% 9% 13% 18% 12%	3014
	11th to 20th	Day	50% 9% 14% 17% 9%	2981
	21st to end	Day	45% 10% 15% 23% 7%	2880
July	1st to 10th	Day	35% 10% 17% 27% 10% 1	2801
	11th to 20th	Day	36% 10% 21% 26% 7%	2746
	21st to end	Day	37% 11% 21% 27% 4	2761
August	1st to 10th	Day	33% 11% 24% 26% 6%	2491
	11th to 20th	Day	36% 12% 25% 24% 3	2469
	21st to end	Day	43% 10% 23% 22% 3	2574
September	1st to 10th	Day	43% 10% 19% 20% 8% 1	2206
	11th to 20th	Day	47% 8% 20% 21% 3	2046
	21st to end	Day	43% 8% 17% 25% 6%	1980
October	1st to 10th	Day	54% 7% 15% 19% 4	1853
	11th to 20th	Day	62% 6% 14% 16% 2	1620
	21st to end	Day	68% 7% 11% 11% 3	1782
November	1st to 10th	Day	72% 6% 12% 6% 4	1464
	11th to 20th	Day	67% 7% 12% 11% 2	1330
	21st to end	Day	67% 7% 13% 11% 2	1330
December	1st to 10th	Day	65% 10% 14% 8% 4	1330
	11th to 20th	Day	63% 8% 15% 9% 4	1487
	21st to end	Day	45% 8% 14% 20% 12% 2	2090
January	1st to 10th	Night	63% 9% 14% 12% 2	5046
	11th to 20th	Night	70% 6% 9% 11% 3	4866
	21st to end	Night	60% 9% 14% 12% 4	4923
February	1st to 10th	Night	56% 6% 13% 16% 8% 1	2660
	11th to 20th	Night	51% 7% 14% 21% 8%	2552
	21st to end	Night	45% 7% 16% 21% 10%	1903
March	1st to 10th	Night	44% 6% 15% 25% 9% 1	3734
	11th to 20th	Night	44% 9% 14% 23% 10%	3645
	21st to end	Night	30% 7% 12% 26% 24% 1	3586
April	1st to 10th	Night	40% 7% 12% 22% 15% 3	1876
	11th to 20th	Night	46% 5% 11% 19% 18% 1	1689
	21st to end	Night	40% 7% 10% 24% 17% 1	1620
May	1st to 10th	Night	44% 9% 14% 22% 10% 1	2417
	11th to 20th	Night	46% 9% 12% 18% 11% 3	2201
	21st to end	Night	50% 8% 15% 18% 9%	2414
June	1st to 10th	Night	44% 8% 12% 22% 14%	1163
	11th to 20th	Night	46% 8% 15% 19% 11% 1	1122
	21st to end	Night	40% 11% 18% 21% 10%	1080
July	1st to 10th	Night	31% 8% 18% 30% 12% 1	1050
	11th to 20th	Night	33% 10% 20% 29% 8%	1088
	21st to end	Night	35% 11% 19% 30% 5%	1314
August	1st to 10th	Night	25% 9% 24% 34% 8%	1424
	11th to 20th	Night	32% 8% 24% 30% 5%	1432
	21st to end	Night	38% 10% 20% 26% 6%	1782
September	1st to 10th	Night	36% 10% 18% 26% 10% 1	1751
	11th to 20th	Night	45% 8% 15% 27% 5%	1914
	21st to end	Night	42% 8% 13% 26% 10%	1980
October	1st to 10th	Night	50% 7% 13% 24% 5%	2087
	11th to 20th	Night	53% 6% 16% 20% 5%	2340
	21st to end	Night	63% 7% 11% 15% 3	2574
November	1st to 10th	Night	69% 7% 10% 9% 3	2613
	11th to 20th	Night	66% 7% 14% 11% 2	2850
	21st to end	Night	66% 8% 12% 11% 3	2850
December	1st to 10th	Night	65% 9% 12% 11% 3	2850
	11th to 20th	Night	60% 7% 15% 12% 6%	3702
	21st to end	Night	47% 6% 13% 21% 13%	5566

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	12% 6% 39% 31% 11% 1	180
	11th to 20th	Day	7% 5% 36% 37% 14% 2	237
	21st to end	Day	20% 6% 25% 33% 15% 1	297
February	1st to 10th	Day	11% 7% 33% 31% 15% 3	270
	11th to 20th	Day	8% 9% 31% 34% 15% 4	270
	21st to end	Day	4 8% 35% 32% 18% 3	225
March	1st to 10th	Day	13% 5% 33% 33% 13% 3	270
	11th to 20th	Day	7% 9% 32% 34% 15% 3	270
	21st to end	Day	11% 11% 31% 27% 16% 3	430
April	1st to 10th	Day	13% 12% 31% 29% 13% 4	483
	11th to 20th	Day	15% 11% 28% 30% 13% 3	640
	21st to end	Day	10% 11% 30% 33% 14% 2	650
May	1st to 10th	Day	17% 9% 30% 27% 15% 1	653
	11th to 20th	Day	12% 13% 31% 25% 15% 4	675
	21st to end	Day	22% 7% 25% 28% 14% 3	734
June	1st to 10th	Day	21% 11% 26% 22% 16% 4	680
	11th to 20th	Day	20% 12% 26% 25% 13% 4	662
	21st to end	Day	17% 9% 25% 28% 15% 5%	630
July	1st to 10th	Day	12% 10% 26% 29% 17% 6%	621
	11th to 20th	Day	15% 7% 25% 29% 16% 7%	618
	21st to end	Day	11% 6% 25% 30% 20% 7%	684
August	1st to 10th	Day	11% 10% 23% 27% 23% 6%	626
	11th to 20th	Day	14% 8% 24% 27% 19% 8%	615
	21st to end	Day	20% 7% 26% 27% 17% 3	693
September	1st to 10th	Day	21% 10% 34% 25% 10% 1	496
	11th to 20th	Day	21% 10% 27% 29% 10% 3	336
	21st to end	Day	14% 15% 29% 27% 14% 1	270
October	1st to 10th	Day	24% 11% 29% 22% 12% 1	270
	11th to 20th	Day	23% 15% 36% 14% 9% 2	270
	21st to end	Day	25% 11% 28% 26% 9% 2	297
November	1st to 10th	Day	18% 11% 29% 29% 11% 2	270
	11th to 20th	Day	20% 10% 33% 30% 6% 1	270
	21st to end	Day	17% 11% 40% 24% 6% 1	270
December	1st to 10th	Day	10% 7% 31% 34% 14% 4	270
	11th to 20th	Day	13% 9% 37% 34% 8%	202
	21st to end	Day	7% 6% 24% 40% 19% 4	198
January	1st to 10th	Night	14% 5% 34% 33% 12% 2	950
	11th to 20th	Night	13% 8% 32% 36% 9% 2	950
	21st to end	Night	19% 7% 34% 29% 10% 1	1045
February	1st to 10th	Night	12% 7% 33% 34% 14% 1	950
	11th to 20th	Night	9% 5% 33% 34% 16% 3	929
	21st to end	Night	7% 6% 31% 35% 19% 2	647
March	1st to 10th	Night	13% 8% 25% 35% 18% 2	760
	11th to 20th	Night	13% 9% 33% 31% 14% 1	670
	21st to end	Night	12% 5% 29% 34% 16% 4	627
April	1st to 10th	Night	13% 5% 26% 34% 19% 2	570
	11th to 20th	Night	16% 5% 29% 31% 17% 2	563
	21st to end	Night	11% 7% 33% 38% 10% 1	570
May	1st to 10th	Night	19% 6% 29% 32% 14% 1	570
	11th to 20th	Night	15% 9% 29% 33% 13% 1	561
	21st to end	Night	20% 6% 27% 34% 12% 1	617
June	1st to 10th	Night	20% 4 26% 30% 18% 1	403
	11th to 20th	Night	20% 7% 21% 36% 14% 2	374
	21st to end	Night	19% 5% 21% 38% 16% 1	360
July	1st to 10th	Night	11% 5% 24% 39% 18% 2	350
	11th to 20th	Night	12% 3 26% 38% 18% 3	392
	21st to end	Night	13% 4 21% 34% 24% 5%	591
August	1st to 10th	Night	8% 6% 24% 36% 23% 3	537
	11th to 20th	Night	14% 5% 22% 29% 27% 4	534
	21st to end	Night	19% 5% 24% 35% 16% 1	594
September	1st to 10th	Night	15% 7% 28% 31% 17% 1	540
	11th to 20th	Night	21% 5% 28% 35% 10% 1	540
	21st to end	Night	18% 6% 31% 35% 10% 1	540
October	1st to 10th	Night	24% 6% 25% 32% 11% 1	647
	11th to 20th	Night	23% 10% 27% 30% 10% 1	900
	21st to end	Night	27% 11% 28% 22% 11% 1	990
November	1st to 10th	Night	22% 9% 32% 27% 9% 1	925
	11th to 20th	Night	19% 9% 34% 26% 10% 1	950
	21st to end	Night	17% 11% 33% 29% 8% 1	950
December	1st to 10th	Night	14% 6% 34% 30% 13% 3	950
	11th to 20th	Night	17% 9% 32% 27% 12% 2	950
	21st to end	Night	16% 4 27% 32% 18% 3	1045

Page generated at 2024-06-14 12:06:12. Version ac07

Copyright © 2024 Attilla Danko.