Fish Lake
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Fish Lake 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	4 9% 4 9% 5% 4 4 3 5% 6% 47%	123749
	Night	3 9% 4 11% 6% 4 4 3 5% 5% 45%	123823
Transparency	Day	33% 6% 10% 18% 21% 13%	123491
	Night	35% 7% 11% 18% 19% 11%	123668
Seeing	Day	11% 14% 27% 27% 17% 5%	15458
	Night	10% 10% 22% 33% 21% 5%	24708

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	4 16% 9% 20% 7% 5% 4 3 4 4 22%	3639
	11th to 20th	Day	2 10% 6% 13% 7% 4 4 4 5% 5% 39%	3640
	21st to end	Day	3 11% 6% 12% 7% 5% 3 2 3 5% 43%	4076
February	1st to 10th	Day	3 13% 6% 15% 6% 5% 6% 5% 6% 8% 29%	1800
	11th to 20th	Day	3 13% 7% 15% 8% 5% 5% 3 4 6% 30%	1934
	21st to end	Day	4 12% 6% 17% 8% 5% 4 4 6% 7% 28%	1650
March	1st to 10th	Day	3 14% 7% 16% 8% 6% 5% 4 6% 6% 26%	4518
	11th to 20th	Day	2 9% 6% 15% 7% 5% 5% 3 5% 5% 38%	4700
	21st to end	Day	2 14% 9% 16% 7% 5% 5% 3 5% 6% 28%	5969
April	1st to 10th	Day	5% 17% 6% 13% 7% 4 5% 4 5% 5% 29%	2400
	11th to 20th	Day	6% 13% 5% 10% 6% 4 4 3 4 7% 38%	2369
	21st to end	Day	7% 12% 5% 9% 6% 4 4 4 6% 7% 37%	2501
May	1st to 10th	Day	5% 9% 5% 8% 4 4 4 3 4 5% 49%	5923
	11th to 20th	Day	5% 10% 4 7% 4 4 4 3 4 6% 50%	6277
	21st to end	Day	5% 9% 2 7% 4 4 4 4 5% 7% 50%	6902
June	1st to 10th	Day	7% 10% 4 8% 4 5% 5% 4 6% 6% 41%	2800
	11th to 20th	Day	8% 8% 2 6% 4 4 4 3 5% 6% 51%	2800
	21st to end	Day	3 4 2 4 4 3 2 2 4 4 67%	2800
July	1st to 10th	Day	2 1 1 3 2 2 2 2 3 3 79%	4491
	11th to 20th	Day	2 3 2 4 3 3 2 2 4 5% 70%	4420
	21st to end	Day	2 2 1 4 3 4 4 3 4 5% 68%	4790
August	1st to 10th	Day	4 4 2 5% 3 3 3 4 6% 7% 58%	4400
	11th to 20th	Day	2 1 1 2 2 2 2 3 5% 5% 75%	3734
	21st to end	Day	3 4 1 3 3 2 2 2 3 5% 72%	4180
September	1st to 10th	Day	4 3 1 4 2 2 3 2 3 5% 71%	2280
	11th to 20th	Day	5% 6% 2 5% 3 4 4 3 4 6% 58%	2203
	21st to end	Day	5% 6% 3 6% 4 3 3 3 4 4 60%	2090
October	1st to 10th	Day	5% 6% 2 5% 3 3 2 2 3 4 65%	3318
	11th to 20th	Day	7% 7% 4 6% 3 3 4 3 5% 6% 53%	3161
	21st to end	Day	4 10% 6% 13% 5% 4 4 3 5% 7% 38%	3118
November	1st to 10th	Day	8% 13% 5% 11% 6% 4 4 4 5% 6% 34%	1764
	11th to 20th	Day	4 13% 5% 12% 7% 5% 5% 4 7% 6% 32%	1800
	21st to end	Day	3 10% 6% 12% 7% 4 5% 4 6% 6% 36%	1650
December	1st to 10th	Day	3 7% 4 10% 5% 4 4 3 4 7% 49%	2620
	11th to 20th	Day	5% 16% 6% 16% 7% 7% 4 4 6% 6% 24%	3028
	21st to end	Day	4 15% 7% 17% 7% 5% 5% 4 6% 7% 22%	4004
January	1st to 10th	Night	4 14% 7% 21% 8% 6% 5% 3 5% 6% 22%	6306
	11th to 20th	Night	2 11% 6% 14% 7% 4 5% 3 4 4 39%	6320
	21st to end	Night	2 9% 4 12% 6% 5% 5% 3 4 5% 43%	6881
February	1st to 10th	Night	4 10% 5% 16% 7% 6% 5% 5% 5% 6% 31%	2600
	11th to 20th	Night	4 10% 6% 16% 8% 7% 4 5% 5% 5% 31%	2353
	21st to end	Night	2 12% 5% 16% 7% 6% 6% 6% 5% 5% 30%	1980
March	1st to 10th	Night	2 13% 6% 13% 7% 5% 6% 4 5% 7% 31%	5376
	11th to 20th	Night	2 9% 6% 18% 7% 5% 4 3 4 5% 37%	5295
	21st to end	Night	2 10% 6% 17% 6% 6% 6% 5% 7% 7% 27%	5006
April	1st to 10th	Night	5% 13% 4 10% 7% 6% 5% 4 5% 6% 36%	2000
	11th to 20th	Night	5% 11% 4 10% 6% 4 4 3 5% 6% 43%	1979
	21st to end	Night	6% 10% 5% 9% 4 4 4 5% 5% 6% 42%	1897
May	1st to 10th	Night	5% 8% 4 10% 4 3 4 3 4 4 50%	4039
	11th to 20th	Night	3 7% 6% 8% 5% 3 3 3 3 5% 53%	3616
	21st to end	Night	4 6% 2 7% 3 3 3 2 4 5% 59%	3972
June	1st to 10th	Night	7% 10% 3 7% 4 4 5% 3 5% 8% 44%	1600
	11th to 20th	Night	7% 6% 3 6% 4 3 3 3 5% 6% 54%	1600
	21st to end	Night	3 4 1 3 4 3 3 3 4 5% 66%	1600
July	1st to 10th	Night	2 1 1 2 3 3 2 2 3 3 78%	2580
	11th to 20th	Night	2 3 1 3 3 2 3 2 3 4 73%	2540
	21st to end	Night	2 4 1 3 3 3 4 2 4 5% 68%	2761
August	1st to 10th	Night	4 5% 2 6% 4 4 4 5% 5% 6% 56%	2529
	11th to 20th	Night	2 2 1 3 2 2 2 3 4 5% 73%	3111
	21st to end	Night	2 4 1 4 2 3 2 2 3 4 73%	3498
September	1st to 10th	Night	2 3 1 3 2 2 2 3 4 5% 72%	1900
	11th to 20th	Night	5% 5% 2 5% 3 3 3 4 3 5% 63%	1976
	21st to end	Night	5% 4 2 5% 3 3 3 2 5% 5% 62%	2090
October	1st to 10th	Night	4 5% 2 6% 3 3 2 2 3 3 67%	3645
	11th to 20th	Night	3 6% 3 8% 4 4 4 3 4 6% 56%	3777
	21st to end	Night	3 7% 4 12% 6% 5% 5% 4 5% 6% 42%	4427
November	1st to 10th	Night	8% 13% 5% 10% 5% 5% 4 4 6% 5% 37%	2535
	11th to 20th	Night	6% 11% 5% 12% 6% 6% 5% 4 7% 7% 32%	2600
	21st to end	Night	3 10% 5% 13% 7% 5% 5% 4 5% 6% 38%	2746
December	1st to 10th	Night	3 6% 3 10% 5% 4 4 3 5% 8% 49%	4560
	11th to 20th	Night	3 15% 6% 17% 7% 7% 7% 4 6% 6% 22%	5176
	21st to end	Night	4 15% 7% 17% 8% 6% 6% 4 5% 5% 22%	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	53% 11% 13% 13% 8% 2	3639
	11th to 20th	Day	39% 11% 11% 21% 11% 6%	3640
	21st to end	Day	40% 9% 10% 15% 14% 12%	4076
February	1st to 10th	Day	47% 9% 15% 20% 8% 1	1800
	11th to 20th	Day	48% 8% 14% 16% 10% 3	1944
	21st to end	Day	48% 8% 12% 16% 11% 4	1650
March	1st to 10th	Day	47% 9% 13% 13% 15% 4	4518
	11th to 20th	Day	37% 7% 13% 26% 15%	4700
	21st to end	Day	43% 10% 18% 20% 8% 1	5969
April	1st to 10th	Day	51% 7% 12% 17% 11% 2	2400
	11th to 20th	Day	41% 5% 13% 21% 17% 3	2372
	21st to end	Day	41% 6% 15% 23% 14% 2	2501
May	1st to 10th	Day	30% 5% 12% 24% 27% 2	5923
	11th to 20th	Day	32% 5% 8% 22% 29% 5%	6280
	21st to end	Day	28% 5% 11% 33% 22% 1	6904
June	1st to 10th	Day	39% 6% 10% 26% 18% 1	2800
	11th to 20th	Day	30% 5% 9% 22% 26% 8%	2800
	21st to end	Day	20% 2 6% 21% 33% 18%	2800
July	1st to 10th	Day	10% 2 3 9% 17% 58%	4422
	11th to 20th	Day	15% 3 5% 7% 19% 50%	4345
	21st to end	Day	16% 3 5% 9% 32% 35%	4639
August	1st to 10th	Day	22% 3 6% 9% 26% 33%	4384
	11th to 20th	Day	9% 2 6% 12% 37% 34%	3770
	21st to end	Day	16% 2 5% 18% 30% 31%	4179
September	1st to 10th	Day	15% 2 5% 12% 34% 32%	2280
	11th to 20th	Day	25% 2 9% 16% 27% 20%	2203
	21st to end	Day	26% 3 8% 18% 29% 16%	2090
October	1st to 10th	Day	24% 2 6% 19% 33% 15%	3318
	11th to 20th	Day	30% 4 10% 21% 28% 6%	3161
	21st to end	Day	39% 7% 10% 22% 19% 4	3118
November	1st to 10th	Day	48% 6% 10% 16% 16% 3	1764
	11th to 20th	Day	46% 7% 15% 18% 12% 2	1800
	21st to end	Day	43% 7% 14% 14% 20% 3	1650
December	1st to 10th	Day	32% 7% 8% 19% 30% 4	2620
	11th to 20th	Day	55% 8% 12% 16% 8% 1	3028
	21st to end	Day	50% 10% 15% 16% 8% 1	4004
January	1st to 10th	Night	50% 13% 13% 14% 8% 1	6306
	11th to 20th	Night	37% 10% 15% 18% 16% 5%	6320
	21st to end	Night	39% 7% 10% 15% 15% 14%	6881
February	1st to 10th	Night	45% 9% 14% 20% 11% 2	2600
	11th to 20th	Night	46% 9% 14% 16% 11% 4	2354
	21st to end	Night	46% 8% 16% 14% 12% 4	1980
March	1st to 10th	Night	42% 7% 14% 15% 16% 6%	5376
	11th to 20th	Night	37% 10% 11% 25% 16%	5295
	21st to end	Night	39% 16% 15% 19% 9% 1	5006
April	1st to 10th	Night	43% 7% 14% 21% 13% 2	2000
	11th to 20th	Night	37% 6% 15% 25% 14% 3	1979
	21st to end	Night	37% 6% 15% 25% 15% 2	1897
May	1st to 10th	Night	27% 4 13% 22% 30% 4	4036
	11th to 20th	Night	30% 5% 7% 28% 25% 4	3616
	21st to end	Night	23% 5% 11% 35% 25% 1	3972
June	1st to 10th	Night	37% 6% 13% 28% 15% 1	1600
	11th to 20th	Night	27% 5% 9% 25% 25% 8%	1600
	21st to end	Night	20% 3 6% 21% 34% 16%	1600
July	1st to 10th	Night	12% 2 4 8% 18% 57%	2540
	11th to 20th	Night	13% 2 5% 8% 21% 52%	2492
	21st to end	Night	17% 3 5% 6% 31% 38%	2674
August	1st to 10th	Night	24% 4 6% 10% 20% 35%	2521
	11th to 20th	Night	13% 3 5% 11% 33% 36%	3141
	21st to end	Night	16% 2 4 20% 30% 28%	3498
September	1st to 10th	Night	14% 2 5% 11% 33% 35%	1900
	11th to 20th	Night	22% 3 7% 19% 27% 22%	1976
	21st to end	Night	23% 2 7% 18% 30% 19%	2090
October	1st to 10th	Night	22% 2 6% 15% 32% 23%	3645
	11th to 20th	Night	25% 5% 14% 21% 28% 6%	3777
	21st to end	Night	37% 7% 11% 16% 24% 6%	4427
November	1st to 10th	Night	45% 5% 11% 16% 18% 5%	2535
	11th to 20th	Night	46% 7% 13% 18% 14% 1	2600
	21st to end	Night	42% 6% 12% 15% 20% 4	2746
December	1st to 10th	Night	30% 7% 11% 17% 28% 7%	4560
	11th to 20th	Night	53% 11% 12% 15% 8% 2	5176
	21st to end	Night	54% 11% 15% 12% 8% 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	24% 18% 23% 19% 13% 4	200
	11th to 20th	Day	6% 19% 27% 24% 16% 8%	200
	21st to end	Day	6% 12% 30% 28% 16% 7%	253
February	1st to 10th	Day	13% 19% 31% 23% 13% 2	400
	11th to 20th	Day	14% 20% 28% 24% 11% 2	488
	21st to end	Day	16% 14% 32% 25% 12% 2	414
March	1st to 10th	Day	14% 21% 32% 23% 10%	500
	11th to 20th	Day	12% 19% 26% 26% 13% 3	500
	21st to end	Day	16% 22% 26% 24% 11% 1	550
April	1st to 10th	Day	16% 19% 26% 23% 13% 2	500
	11th to 20th	Day	13% 18% 29% 23% 14% 3	492
	21st to end	Day	13% 20% 25% 25% 15% 3	500
May	1st to 10th	Day	12% 18% 26% 25% 14% 4	503
	11th to 20th	Day	24% 14% 21% 20% 16% 5%	528
	21st to end	Day	17% 10% 21% 25% 19% 8%	573
June	1st to 10th	Day	10% 15% 23% 25% 20% 8%	530
	11th to 20th	Day	15% 18% 29% 23% 11% 4	530
	21st to end	Day	5% 11% 26% 33% 21% 5%	530
July	1st to 10th	Day	4 6% 32% 36% 17% 5%	507
	11th to 20th	Day	3 8% 32% 36% 17% 4	484
	21st to end	Day	3 4 28% 37% 20% 6%	531
August	1st to 10th	Day	7% 6% 26% 33% 21% 7%	487
	11th to 20th	Day	4 7% 26% 31% 23% 8%	477
	21st to end	Day	5% 7% 27% 30% 22% 7%	539
September	1st to 10th	Day	7% 7% 24% 34% 22% 6%	490
	11th to 20th	Day	9% 10% 25% 29% 22% 6%	490
	21st to end	Day	7% 10% 27% 29% 23% 4	490
October	1st to 10th	Day	14% 13% 23% 26% 18% 6%	490
	11th to 20th	Day	11% 14% 25% 28% 18% 4	490
	21st to end	Day	12% 17% 28% 23% 16% 4	347
November	1st to 10th	Day	16% 14% 26% 25% 17% 2	300
	11th to 20th	Day	12% 18% 26% 23% 17% 4	300
	21st to end	Day	12% 14% 22% 29% 19% 4	225
December	1st to 10th	Day	10% 16% 21% 23% 20% 11%	200
	11th to 20th	Day	21% 15% 27% 22% 14% 2	200
	21st to end	Day	17% 15% 24% 25% 15% 4	220
January	1st to 10th	Night	12% 15% 26% 25% 18% 5%	800
	11th to 20th	Night	8% 14% 26% 27% 19% 6%	800
	21st to end	Night	9% 10% 24% 31% 20% 7%	880
February	1st to 10th	Night	12% 14% 27% 27% 17% 3	800
	11th to 20th	Night	10% 13% 28% 28% 17% 3	784
	21st to end	Night	8% 13% 28% 34% 15% 2	660
March	1st to 10th	Night	9% 14% 31% 28% 15% 3	800
	11th to 20th	Night	12% 12% 24% 30% 18% 3	800
	21st to end	Night	12% 15% 26% 33% 13% 1	880
April	1st to 10th	Night	11% 10% 27% 32% 17% 3	800
	11th to 20th	Night	10% 14% 25% 29% 17% 5%	791
	21st to end	Night	12% 11% 23% 34% 18% 2	697
May	1st to 10th	Night	10% 15% 26% 29% 19% 2	578
	11th to 20th	Night	12% 12% 18% 29% 25% 5%	394
	21st to end	Night	13% 7% 18% 30% 26% 6%	433
June	1st to 10th	Night	12% 7% 16% 39% 23% 4	400
	11th to 20th	Night	11% 7% 26% 35% 19% 3	400
	21st to end	Night	5% 4 19% 44% 27% 3	400
July	1st to 10th	Night	4 3 16% 44% 28% 4	380
	11th to 20th	Night	2 2 17% 54% 23% 3	368
	21st to end	Night	3 1 14% 50% 29% 4	416
August	1st to 10th	Night	7% 2 12% 49% 28% 3	378
	11th to 20th	Night	3 3 12% 42% 37% 5%	737
	21st to end	Night	5% 2 16% 42% 31% 4	836
September	1st to 10th	Night	4 3 13% 42% 33% 5%	760
	11th to 20th	Night	7% 4 13% 34% 31% 12%	760
	21st to end	Night	8% 4 17% 32% 28% 11%	760
October	1st to 10th	Night	11% 5% 20% 36% 21% 7%	760
	11th to 20th	Night	6% 9% 19% 34% 24% 8%	760
	21st to end	Night	10% 10% 20% 32% 19% 8%	836
November	1st to 10th	Night	15% 11% 19% 30% 21% 4	780
	11th to 20th	Night	14% 12% 27% 29% 16% 3	800
	21st to end	Night	10% 13% 22% 32% 18% 6%	800
December	1st to 10th	Night	9% 13% 23% 30% 20% 5%	800
	11th to 20th	Night	12% 13% 26% 28% 17% 4	800
	21st to end	Night	15% 19% 26% 27% 11% 2	880

Page generated at 2025-07-02 22:30:13. Version ac07

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