Chiloquin
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Chiloquin clear sky chart from 2005-11-06 to 2025-07-06.

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% 9% 2 5% 4 4 4 3 5% 6% 53%	124204
	Night	7% 9% 2 6% 4 4 4 3 5% 6% 50%	123422
Transparency	Day	32% 4 9% 21% 21% 12%	123951
	Night	36% 5% 11% 22% 18% 9%	123262
Seeing	Day	15% 12% 22% 24% 19% 8%	15648
	Night	11% 7% 16% 37% 25% 3	24754

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	13% 18% 5% 9% 7% 6% 5% 4 6% 6% 21%	3639
	11th to 20th	Day	12% 15% 3 6% 4 3 3 2 4 5% 43%	3686
	21st to end	Day	10% 11% 2 6% 5% 4 4 3 4 6% 45%	4510
February	1st to 10th	Day	8% 13% 3 8% 5% 6% 6% 4 7% 8% 32%	1800
	11th to 20th	Day	9% 15% 4 8% 5% 4 4 3 5% 7% 36%	1760
	21st to end	Day	6% 16% 4 8% 6% 5% 5% 3 6% 7% 33%	1650
March	1st to 10th	Day	8% 17% 4 8% 5% 4 4 3 5% 6% 35%	4686
	11th to 20th	Day	6% 18% 4 8% 5% 4 4 3 4 5% 38%	5000
	21st to end	Day	10% 18% 3 9% 6% 5% 4 3 5% 7% 28%	5656
April	1st to 10th	Day	7% 14% 4 9% 6% 4 5% 4 6% 6% 35%	2400
	11th to 20th	Day	8% 13% 4 6% 5% 4 4 3 5% 6% 42%	2369
	21st to end	Day	6% 9% 3 6% 4 4 4 3 5% 8% 47%	2445
May	1st to 10th	Day	7% 8% 2 4 3 3 3 3 5% 6% 57%	6133
	11th to 20th	Day	5% 6% 2 5% 3 4 4 3 5% 6% 58%	6277
	21st to end	Day	4 4 1 3 3 3 3 3 5% 7% 64%	6902
June	1st to 10th	Day	7% 6% 2 5% 4 4 4 4 6% 8% 50%	2800
	11th to 20th	Day	4 3 2 4 4 3 3 3 5% 7% 64%	2800
	21st to end	Day	4 2 1 3 2 2 2 2 3 6% 72%	2800
July	1st to 10th	Day	1 1 1 1 1 1 1 2 3 87%	4491
	11th to 20th	Day	2 2 1 2 2 2 2 2 3 3 80%	4420
	21st to end	Day	1 1 1 1 1 1 1 2 3 87%	4708
August	1st to 10th	Day	3 2 1 2 2 2 3 2 4 5% 73%	4091
	11th to 20th	Day	1 1 1 2 2 2 2 2 3 4 80%	3995
	21st to end	Day	3 2 1 2 2 2 2 2 3 4 78%	4180
September	1st to 10th	Day	1 1 1 2 2 2 2 2 3 4 80%	2280
	11th to 20th	Day	4 3 2 4 3 3 3 4 5% 6% 64%	2280
	21st to end	Day	4 3 1 5% 3 3 3 2 4 6% 65%	2022
October	1st to 10th	Day	4 3 1 3 2 2 3 2 3 5% 73%	3180
	11th to 20th	Day	6% 5% 2 4 4 4 4 3 7% 8% 53%	3161
	21st to end	Day	9% 9% 2 6% 4 4 5% 3 5% 8% 44%	3417
November	1st to 10th	Day	11% 10% 3 7% 5% 5% 5% 4 5% 7% 38%	1764
	11th to 20th	Day	10% 11% 3 8% 6% 6% 5% 5% 6% 8% 31%	1650
	21st to end	Day	7% 13% 2 7% 7% 5% 6% 4 6% 8% 35%	1600
December	1st to 10th	Day	6% 7% 2 5% 5% 5% 4 4 6% 9% 47%	2620
	11th to 20th	Day	16% 16% 4 9% 5% 6% 5% 4 5% 8% 21%	3028
	21st to end	Day	9% 16% 5% 13% 9% 7% 7% 5% 5% 6% 17%	4004
January	1st to 10th	Night	14% 16% 4 8% 6% 7% 6% 5% 6% 7% 22%	6306
	11th to 20th	Night	9% 12% 4 7% 5% 4 4 2 3 4 46%	6260
	21st to end	Night	12% 12% 4 7% 5% 5% 5% 3 4 5% 39%	6468
February	1st to 10th	Night	8% 10% 3 7% 6% 5% 6% 5% 8% 8% 35%	2600
	11th to 20th	Night	8% 13% 3 7% 6% 5% 6% 4 5% 5% 38%	2526
	21st to end	Night	6% 13% 4 7% 5% 4 5% 5% 6% 8% 37%	1980
March	1st to 10th	Night	7% 14% 4 7% 5% 5% 5% 5% 7% 8% 35%	5205
	11th to 20th	Night	6% 13% 4 6% 4 4 5% 4 5% 6% 43%	5000
	21st to end	Night	6% 16% 4 9% 6% 6% 6% 5% 7% 7% 28%	5319
April	1st to 10th	Night	9% 11% 3 8% 5% 5% 4 4 6% 7% 38%	2000
	11th to 20th	Night	5% 10% 4 6% 6% 4 3 3 5% 7% 47%	1979
	21st to end	Night	7% 8% 2 5% 3 4 4 4 6% 8% 48%	1950
May	1st to 10th	Night	8% 8% 2 4 3 3 3 2 3 4 60%	3834
	11th to 20th	Night	3 8% 2 5% 3 4 4 3 4 5% 60%	3616
	21st to end	Night	4 4 1 3 2 2 2 2 4 5% 71%	3972
June	1st to 10th	Night	8% 7% 2 4 4 4 4 3 5% 7% 53%	1600
	11th to 20th	Night	5% 4 1 3 2 2 3 3 4 5% 67%	1600
	21st to end	Night	4 3 1 2 2 2 2 2 3 4 75%	1600
July	1st to 10th	Night	1 1 1 1 1 1 1 2 3 87%	2580
	11th to 20th	Night	1 1 1 1 2 2 2 2 3 4 81%	2540
	21st to end	Night	1 1 2 1 1 2 2 3 3 83%	2843
August	1st to 10th	Night	2 2 1 2 2 2 3 3 5% 5% 73%	2848
	11th to 20th	Night	1 1 1 2 2 2 2 2 3 5% 79%	2844
	21st to end	Night	4 2 1 2 1 1 2 2 3 4 79%	3498
September	1st to 10th	Night	1 1 1 1 1 1 2 3 5% 82%	1900
	11th to 20th	Night	3 3 1 2 2 2 3 3 4 7% 70%	1900
	21st to end	Night	6% 4 1 3 2 2 2 2 3 5% 69%	2154
October	1st to 10th	Night	3 2 1 2 3 3 3 2 3 4 75%	3800
	11th to 20th	Night	7% 5% 1 5% 4 3 3 3 4 7% 59%	3777
	21st to end	Night	6% 8% 2 5% 4 4 5% 4 6% 8% 47%	4151
November	1st to 10th	Night	11% 10% 2 6% 5% 5% 5% 4 5% 7% 40%	2535
	11th to 20th	Night	12% 9% 2 7% 5% 6% 6% 5% 6% 8% 33%	2749
	21st to end	Night	8% 11% 3 6% 5% 4 5% 4 6% 8% 40%	2800
December	1st to 10th	Night	6% 6% 2 5% 4 4 3 3 6% 8% 54%	4560
	11th to 20th	Night	11% 15% 5% 10% 7% 6% 7% 5% 7% 7% 22%	5176
	21st to end	Night	11% 16% 4 11% 7% 7% 5% 4 6% 6% 23%	6952

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	62% 6% 11% 15% 6%	3639
	11th to 20th	Day	45% 4 7% 23% 17% 3	3686
	21st to end	Day	41% 6% 9% 12% 21% 12%	4510
February	1st to 10th	Day	47% 8% 15% 19% 10% 1	1800
	11th to 20th	Day	49% 6% 14% 17% 12% 2	1769
	21st to end	Day	51% 6% 12% 15% 13% 3	1650
March	1st to 10th	Day	50% 4 10% 23% 10% 3	4686
	11th to 20th	Day	48% 4 11% 19% 17%	5000
	21st to end	Day	53% 7% 13% 20% 6%	5656
April	1st to 10th	Day	50% 6% 11% 19% 11% 3	2400
	11th to 20th	Day	42% 5% 14% 20% 15% 4	2372
	21st to end	Day	35% 7% 15% 26% 16% 2	2445
May	1st to 10th	Day	28% 4 9% 28% 25% 6%	6133
	11th to 20th	Day	27% 3 10% 23% 30% 6%	6280
	21st to end	Day	20% 4 12% 44% 18% 1	6904
June	1st to 10th	Day	32% 6% 13% 28% 20% 2	2800
	11th to 20th	Day	21% 5% 9% 30% 27% 7%	2800
	21st to end	Day	16% 3 8% 25% 32% 15%	2800
July	1st to 10th	Day	7% 1 4 12% 19% 57%	4422
	11th to 20th	Day	12% 3 3 10% 21% 52%	4345
	21st to end	Day	6% 1 3 13% 39% 37%	4559
August	1st to 10th	Day	15% 3 4 13% 30% 35%	4076
	11th to 20th	Day	9% 2 4 24% 42% 19%	4034
	21st to end	Day	12% 2 5% 26% 31% 23%	4179
September	1st to 10th	Day	10% 2 5% 17% 34% 32%	2280
	11th to 20th	Day	21% 4 8% 22% 30% 15%	2280
	21st to end	Day	22% 2 9% 23% 28% 16%	2022
October	1st to 10th	Day	18% 2 9% 16% 32% 22%	3180
	11th to 20th	Day	28% 4 16% 30% 16% 5%	3161
	21st to end	Day	40% 6% 8% 25% 18% 4	3417
November	1st to 10th	Day	45% 7% 12% 20% 14% 3	1764
	11th to 20th	Day	49% 8% 16% 13% 12% 1	1650
	21st to end	Day	46% 6% 14% 15% 16% 3	1600
December	1st to 10th	Day	33% 5% 9% 25% 24% 3	2620
	11th to 20th	Day	61% 6% 15% 13% 4	3028
	21st to end	Day	66% 8% 10% 12% 4	4004
January	1st to 10th	Night	59% 8% 11% 15% 7% 1	6306
	11th to 20th	Night	41% 6% 8% 22% 19% 5%	6260
	21st to end	Night	46% 5% 8% 10% 16% 14%	6468
February	1st to 10th	Night	45% 7% 15% 19% 13% 2	2600
	11th to 20th	Night	47% 6% 13% 19% 13% 2	2528
	21st to end	Night	45% 8% 14% 18% 12% 3	1980
March	1st to 10th	Night	46% 6% 12% 23% 9% 4	5205
	11th to 20th	Night	42% 5% 12% 25% 16%	5000
	21st to end	Night	52% 11% 13% 17% 7%	5319
April	1st to 10th	Night	46% 7% 16% 20% 10% 1	2000
	11th to 20th	Night	38% 5% 16% 22% 15% 4	1979
	21st to end	Night	35% 8% 17% 26% 12% 2	1950
May	1st to 10th	Night	28% 4 9% 27% 28% 3	3831
	11th to 20th	Night	27% 4 13% 29% 25% 2	3616
	21st to end	Night	18% 4 18% 49% 11% 1	3972
June	1st to 10th	Night	32% 6% 15% 28% 17% 1	1600
	11th to 20th	Night	20% 4 13% 34% 24% 6%	1600
	21st to end	Night	16% 3 9% 33% 31% 9%	1600
July	1st to 10th	Night	6% 1 6% 15% 20% 52%	2540
	11th to 20th	Night	10% 2 3 12% 29% 44%	2492
	21st to end	Night	10% 2 4 13% 40% 31%	2754
August	1st to 10th	Night	14% 3 6% 16% 35% 26%	2839
	11th to 20th	Night	10% 3 4 33% 33% 17%	2871
	21st to end	Night	13% 2 7% 29% 26% 22%	3498
September	1st to 10th	Night	7% 2 4 21% 35% 31%	1900
	11th to 20th	Night	16% 4 10% 26% 28% 16%	1900
	21st to end	Night	20% 3 8% 26% 25% 19%	2154
October	1st to 10th	Night	16% 3 8% 19% 31% 23%	3800
	11th to 20th	Night	28% 3 13% 33% 17% 5%	3777
	21st to end	Night	35% 5% 9% 28% 16% 5%	4151
November	1st to 10th	Night	45% 5% 13% 18% 15% 4	2535
	11th to 20th	Night	48% 8% 13% 18% 13% 1	2749
	21st to end	Night	42% 7% 13% 18% 16% 4	2800
December	1st to 10th	Night	30% 5% 8% 22% 32% 3	4560
	11th to 20th	Night	60% 6% 13% 15% 5%	5176
	21st to end	Night	59% 8% 12% 14% 6% 1	6952

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	28% 14% 24% 21% 12% 3	200
	11th to 20th	Day	27% 6% 20% 26% 14% 7%	220
	21st to end	Day	19% 13% 22% 18% 20% 9%	440
February	1st to 10th	Day	20% 16% 24% 22% 14% 5%	400
	11th to 20th	Day	25% 18% 21% 18% 14% 5%	398
	21st to end	Day	23% 15% 24% 24% 12% 3	414
March	1st to 10th	Day	27% 18% 23% 22% 9% 2	500
	11th to 20th	Day	24% 16% 23% 20% 13% 3	500
	21st to end	Day	27% 19% 23% 20% 8% 3	550
April	1st to 10th	Day	22% 17% 26% 19% 13% 4	500
	11th to 20th	Day	21% 19% 24% 22% 10% 4	492
	21st to end	Day	17% 18% 24% 20% 16% 5%	500
May	1st to 10th	Day	16% 15% 28% 23% 13% 5%	503
	11th to 20th	Day	21% 15% 22% 20% 16% 6%	528
	21st to end	Day	15% 11% 21% 24% 19% 10%	573
June	1st to 10th	Day	11% 16% 24% 21% 20% 9%	530
	11th to 20th	Day	11% 17% 24% 24% 18% 5%	530
	21st to end	Day	4 9% 23% 26% 27% 10%	530
July	1st to 10th	Day	3 8% 27% 30% 22% 10%	507
	11th to 20th	Day	1 7% 27% 30% 25% 10%	484
	21st to end	Day	3 6% 21% 29% 30% 12%	531
August	1st to 10th	Day	2 4 25% 29% 27% 14%	487
	11th to 20th	Day	4 6% 19% 30% 22% 20%	477
	21st to end	Day	4 5% 20% 27% 29% 14%	539
September	1st to 10th	Day	2 5% 21% 28% 29% 14%	490
	11th to 20th	Day	8% 8% 20% 28% 24% 12%	490
	21st to end	Day	8% 11% 21% 28% 23% 10%	490
October	1st to 10th	Day	11% 11% 21% 22% 21% 13%	490
	11th to 20th	Day	17% 9% 17% 20% 25% 12%	490
	21st to end	Day	18% 11% 22% 21% 16% 13%	520
November	1st to 10th	Day	19% 10% 18% 30% 14% 9%	300
	11th to 20th	Day	18% 9% 20% 21% 23% 8%	225
	21st to end	Day	19% 12% 14% 22% 26% 8%	200
December	1st to 10th	Day	20% 10% 16% 25% 17% 13%	200
	11th to 20th	Day	28% 11% 21% 22% 15% 5%	200
	21st to end	Day	27% 10% 23% 23% 15% 2	220
January	1st to 10th	Night	18% 10% 19% 34% 16% 3	800
	11th to 20th	Night	14% 10% 19% 34% 21% 2	800
	21st to end	Night	14% 8% 18% 36% 21% 3	880
February	1st to 10th	Night	14% 8% 20% 38% 18% 1	800
	11th to 20th	Night	14% 9% 21% 36% 18% 1	784
	21st to end	Night	13% 12% 20% 38% 16% 1	660
March	1st to 10th	Night	17% 12% 21% 34% 15% 2	800
	11th to 20th	Night	15% 11% 19% 33% 21% 1	800
	21st to end	Night	16% 13% 21% 34% 15%	880
April	1st to 10th	Night	15% 11% 20% 37% 16% 2	800
	11th to 20th	Night	9% 13% 25% 31% 19% 3	791
	21st to end	Night	11% 10% 19% 36% 22% 2	750
May	1st to 10th	Night	11% 4 21% 39% 23% 2	490
	11th to 20th	Night	8% 7% 17% 34% 31% 3	394
	21st to end	Night	10% 6% 16% 37% 29% 3	433
June	1st to 10th	Night	12% 4 13% 39% 31% 1	400
	11th to 20th	Night	7% 4 17% 51% 22%	400
	21st to end	Night	5% 2 9% 47% 37%	400
July	1st to 10th	Night	3 1 8% 44% 44% 1	380
	11th to 20th	Night	1 7% 56% 35%	368
	21st to end	Night	2 1 3 48% 44% 3	462
August	1st to 10th	Night	2 3 42% 48% 5%	567
	11th to 20th	Night	1 1 5% 37% 51% 6%	583
	21st to end	Night	3 2 12% 42% 39% 2	836
September	1st to 10th	Night	2 2 12% 40% 41% 3	760
	11th to 20th	Night	4 4 12% 36% 39% 6%	760
	21st to end	Night	7% 3 13% 39% 33% 6%	760
October	1st to 10th	Night	7% 5% 15% 38% 32% 4	760
	11th to 20th	Night	11% 5% 12% 36% 32% 4	760
	21st to end	Night	13% 6% 14% 37% 25% 6%	836
November	1st to 10th	Night	16% 6% 17% 39% 20% 3	780
	11th to 20th	Night	16% 9% 18% 38% 17% 2	800
	21st to end	Night	13% 10% 18% 34% 22% 3	800
December	1st to 10th	Night	16% 8% 16% 35% 22% 4	800
	11th to 20th	Night	18% 9% 16% 37% 18% 2	800
	21st to end	Night	21% 13% 21% 34% 10% 1	880

Page generated at 2025-07-02 22:30:15. Version ac07

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