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 2026-10-29.

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 8% 4 9% 5% 4 4 3 5% 6% 50%	158265
	Night	3 8% 4 11% 5% 4 4 3 5% 6% 46%	151176
Transparency	Day	31% 6% 9% 18% 21% 14%	153099
	Night	33% 7% 10% 18% 20% 12%	147337
Seeing	Day	12% 14% 27% 27% 16% 4	17189
	Night	10% 10% 22% 33% 20% 4	26356

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% 21% 8% 5% 4 3 4 4 21%	4722
	11th to 20th	Day	2 8% 4 10% 5% 3 4 3 5% 5% 50%	4740
	21st to end	Day	2 9% 5% 13% 7% 6% 5% 3 4 6% 40%	5287
February	1st to 10th	Day	3 12% 5% 15% 6% 5% 6% 5% 6% 8% 29%	1890
	11th to 20th	Day	3 13% 7% 15% 8% 6% 5% 3 4 6% 29%	2033
	21st to end	Day	4 13% 6% 16% 8% 5% 5% 5% 5% 7% 27%	1730
March	1st to 10th	Day	3 14% 7% 16% 8% 6% 5% 4 6% 6% 26%	4618
	11th to 20th	Day	2 9% 6% 15% 7% 5% 5% 3 5% 5% 38%	4803
	21st to end	Day	2 14% 9% 16% 7% 5% 5% 3 5% 7% 28%	6101
April	1st to 10th	Day	5% 17% 6% 13% 7% 4 5% 3 5% 5% 29%	2520
	11th to 20th	Day	6% 13% 5% 10% 6% 4 4 3 5% 7% 37%	2489
	21st to end	Day	7% 12% 5% 9% 6% 4 4 4 6% 7% 37%	2626
May	1st to 10th	Day	4 7% 4 8% 4 4 4 3 4 6% 52%	7681
	11th to 20th	Day	4 8% 4 7% 4 4 4 3 5% 6% 53%	8160
	21st to end	Day	5% 8% 3 7% 4 4 4 3 5% 7% 49%	8992
June	1st to 10th	Day	7% 10% 4 8% 4 5% 5% 4 6% 6% 42%	2940
	11th to 20th	Day	7% 8% 2 6% 4 3 4 3 5% 6% 52%	2940
	21st to end	Day	3 4 2 4 4 4 2 2 4 4 66%	2940
July	1st to 10th	Day	2 2 1 3 2 2 2 2 4 5% 74%	8219
	11th to 20th	Day	3 4 2 4 3 3 3 2 4 5% 66%	8220
	21st to end	Day	3 3 1 4 3 4 5% 4 5% 6% 61%	8922
August	1st to 10th	Day	2 3 1 4 3 3 3 3 5% 7% 67%	8110
	11th to 20th	Day	1 2 1 3 3 3 3 3 5% 6% 71%	7011
	21st to end	Day	5% 5% 2 5% 4 3 3 3 5% 6% 58%	7750
September	1st to 10th	Day	5% 3 1 4 3 3 3 2 4 6% 67%	2520
	11th to 20th	Day	4 6% 2 5% 4 4 4 3 4 6% 59%	2435
	21st to end	Day	5% 6% 3 6% 4 3 2 3 4 4 61%	2310
October	1st to 10th	Day	5% 6% 2 5% 3 3 2 2 3 4 64%	3528
	11th to 20th	Day	6% 7% 4 6% 3 3 4 3 5% 6% 53%	3361
	21st to end	Day	4 10% 6% 13% 5% 4 4 3 5% 7% 38%	3291
November	1st to 10th	Day	7% 13% 6% 10% 5% 4 4 4 5% 6% 34%	1854
	11th to 20th	Day	4 13% 4 11% 7% 5% 5% 4 7% 6% 31%	1890
	21st to end	Day	3 9% 6% 12% 7% 4 5% 4 6% 6% 37%	1732
December	1st to 10th	Day	3 7% 4 10% 5% 4 4 3 4 7% 48%	2700
	11th to 20th	Day	5% 15% 6% 16% 7% 7% 4 4 6% 6% 24%	3108
	21st to end	Day	4 15% 7% 16% 7% 5% 5% 4 6% 7% 22%	4092
January	1st to 10th	Night	4 13% 7% 23% 9% 6% 5% 3 5% 6% 21%	8172
	11th to 20th	Night	2 8% 5% 11% 5% 4 5% 3 4 4 50%	8220
	21st to end	Night	2 9% 4 13% 6% 6% 5% 4 5% 6% 40%	8897
February	1st to 10th	Night	4 10% 4 17% 7% 6% 5% 5% 4 6% 31%	2730
	11th to 20th	Night	4 10% 5% 16% 8% 7% 5% 4 5% 6% 30%	2474
	21st to end	Night	2 12% 5% 16% 8% 6% 6% 5% 5% 5% 29%	2076
March	1st to 10th	Night	2 13% 6% 14% 7% 5% 6% 4 5% 7% 31%	5496
	11th to 20th	Night	2 9% 6% 17% 7% 5% 4 3 4 5% 37%	5412
	21st to end	Night	2 10% 6% 17% 6% 6% 6% 5% 7% 7% 27%	5116
April	1st to 10th	Night	4 12% 4 10% 7% 6% 5% 4 5% 6% 36%	2100
	11th to 20th	Night	5% 11% 4 10% 6% 4 4 3 5% 6% 42%	2079
	21st to end	Night	6% 10% 5% 9% 4 4 4 4 5% 6% 42%	1992
May	1st to 10th	Night	4 7% 3 9% 4 3 4 3 5% 6% 51%	5247
	11th to 20th	Night	3 7% 5% 7% 4 3 3 3 4 6% 55%	4700
	21st to end	Night	5% 7% 3 6% 3 3 3 3 5% 6% 57%	5181
June	1st to 10th	Night	7% 10% 4 7% 4 4 5% 3 5% 8% 45%	1680
	11th to 20th	Night	7% 6% 2 5% 4 3 3 3 5% 6% 55%	1680
	21st to end	Night	3 5% 1 4 4 3 3 3 4 5% 64%	1680
July	1st to 10th	Night	2 2 1 3 3 3 3 2 3 4 75%	4740
	11th to 20th	Night	3 3 2 4 3 2 3 2 3 4 71%	4740
	21st to end	Night	2 4 2 5% 5% 4 4 3 5% 5% 61%	5153
August	1st to 10th	Night	2 4 1 4 3 3 3 3 5% 6% 64%	4682
	11th to 20th	Night	2 2 1 4 3 3 3 3 5% 6% 68%	5871
	21st to end	Night	4 5% 2 6% 4 4 3 3 4 5% 60%	6499
September	1st to 10th	Night	3 3 1 4 3 2 3 3 4 5% 68%	2100
	11th to 20th	Night	5% 5% 2 4 3 3 3 4 3 5% 63%	2184
	21st to end	Night	5% 4 2 5% 3 3 3 3 5% 5% 62%	2310
October	1st to 10th	Night	4 5% 2 6% 3 3 2 2 3 3 68%	3875
	11th to 20th	Night	3 6% 3 8% 4 4 4 4 4 6% 56%	4017
	21st to end	Night	3 7% 4 12% 6% 5% 5% 4 5% 6% 42%	4672
November	1st to 10th	Night	7% 13% 5% 10% 5% 5% 4 4 6% 5% 37%	2665
	11th to 20th	Night	6% 11% 5% 12% 6% 6% 5% 4 7% 7% 31%	2730
	21st to end	Night	3 10% 5% 13% 7% 5% 5% 4 5% 6% 38%	2884
December	1st to 10th	Night	3 6% 3 10% 5% 4 4 3 5% 8% 48%	4700
	11th to 20th	Night	3 14% 6% 16% 7% 7% 7% 4 6% 6% 22%	5316
	21st to end	Night	4 15% 7% 17% 8% 6% 6% 4 5% 5% 22%	7106

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	52% 13% 14% 13% 6% 1	4723
	11th to 20th	Day	30% 9% 9% 17% 20% 14%	4740
	21st to end	Day	39% 9% 10% 14% 15% 13%	5287
February	1st to 10th	Day	45% 9% 15% 20% 10% 1	1890
	11th to 20th	Day	48% 8% 15% 16% 10% 3	2043
	21st to end	Day	48% 9% 12% 16% 11% 4	1730
March	1st to 10th	Day	47% 9% 13% 13% 14% 4	4618
	11th to 20th	Day	37% 7% 13% 26% 15% 1	4803
	21st to end	Day	43% 10% 18% 20% 8% 1	6101
April	1st to 10th	Day	50% 7% 12% 19% 11% 2	2520
	11th to 20th	Day	42% 5% 13% 21% 17% 2	2492
	21st to end	Day	41% 6% 14% 22% 15% 2	2626
May	1st to 10th	Day	26% 5% 10% 25% 30% 3	7681
	11th to 20th	Day	28% 5% 8% 24% 30% 6%	8163
	21st to end	Day	29% 5% 10% 33% 20% 2	8994
June	1st to 10th	Day	38% 6% 10% 25% 19% 2	2940
	11th to 20th	Day	29% 5% 9% 21% 27% 9%	2940
	21st to end	Day	21% 2 6% 21% 33% 17%	2940
July	1st to 10th	Day	12% 3 4 12% 28% 42%	8151
	11th to 20th	Day	18% 4 5% 9% 21% 45%	8145
	21st to end	Day	20% 4 6% 14% 22% 33%	8723
August	1st to 10th	Day	16% 2 5% 8% 26% 44%	6424
	11th to 20th	Day	13% 3 6% 19% 34% 25%	5527
	21st to end	Day	21% 3 5% 18% 30% 22%	6077
September	1st to 10th	Day	18% 3 5% 12% 33% 29%	2520
	11th to 20th	Day	24% 3 9% 17% 28% 19%	2435
	21st to end	Day	25% 3 7% 19% 29% 16%	2310
October	1st to 10th	Day	24% 3 6% 19% 34% 15%	3528
	11th to 20th	Day	29% 4 10% 21% 28% 7%	3361
	21st to end	Day	39% 7% 10% 23% 18% 4	3291
November	1st to 10th	Day	46% 7% 11% 17% 16% 3	1854
	11th to 20th	Day	46% 7% 15% 18% 12% 2	1890
	21st to end	Day	42% 7% 14% 15% 19% 3	1732
December	1st to 10th	Day	33% 7% 9% 18% 29% 4	2700
	11th to 20th	Day	54% 8% 11% 16% 8% 1	3108
	21st to end	Day	50% 10% 15% 16% 8% 1	4092
January	1st to 10th	Night	48% 16% 13% 16% 6% 1	8172
	11th to 20th	Night	30% 8% 12% 15% 21% 15%	8220
	21st to end	Night	40% 7% 10% 13% 14% 16%	8897
February	1st to 10th	Night	45% 8% 13% 20% 12% 2	2730
	11th to 20th	Night	46% 9% 14% 16% 11% 4	2475
	21st to end	Night	47% 8% 16% 14% 12% 4	2076
March	1st to 10th	Night	42% 7% 14% 15% 16% 6%	5496
	11th to 20th	Night	37% 10% 12% 25% 16% 1	5412
	21st to end	Night	39% 16% 16% 19% 10% 1	5116
April	1st to 10th	Night	42% 7% 14% 22% 13% 2	2100
	11th to 20th	Night	39% 6% 14% 24% 14% 3	2079
	21st to end	Night	37% 6% 15% 24% 16% 2	1992
May	1st to 10th	Night	24% 4 12% 25% 30% 5%	5245
	11th to 20th	Night	27% 5% 7% 31% 26% 4	4700
	21st to end	Night	25% 5% 11% 33% 25% 2	5182
June	1st to 10th	Night	37% 5% 12% 27% 16% 2	1680
	11th to 20th	Night	27% 5% 8% 24% 26% 9%	1680
	21st to end	Night	21% 3 6% 21% 33% 16%	1680
July	1st to 10th	Night	13% 2 4 11% 26% 44%	4700
	11th to 20th	Night	16% 2 4 9% 20% 48%	4692
	21st to end	Night	22% 4 5% 11% 20% 37%	5040
August	1st to 10th	Night	17% 3 5% 8% 20% 48%	3701
	11th to 20th	Night	15% 4 4 17% 32% 28%	4621
	21st to end	Night	21% 3 4 20% 32% 20%	5092
September	1st to 10th	Night	17% 3 5% 11% 33% 32%	2100
	11th to 20th	Night	21% 3 8% 19% 29% 21%	2184
	21st to end	Night	22% 3 7% 19% 30% 19%	2310
October	1st to 10th	Night	22% 2 6% 15% 32% 22%	3875
	11th to 20th	Night	25% 5% 14% 22% 28% 7%	4017
	21st to end	Night	36% 7% 11% 17% 25% 5%	4672
November	1st to 10th	Night	44% 6% 12% 17% 17% 4	2665
	11th to 20th	Night	46% 7% 13% 18% 14% 1	2730
	21st to end	Night	42% 7% 12% 16% 20% 4	2884
December	1st to 10th	Night	31% 7% 11% 17% 27% 7%	4700
	11th to 20th	Night	52% 11% 12% 15% 8% 2	5316
	21st to end	Night	54% 11% 15% 12% 8% 1	7106

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	27% 18% 22% 19% 12% 3	220
	11th to 20th	Day	5% 17% 26% 25% 17% 8%	220
	21st to end	Day	5% 13% 32% 28% 15% 6%	277
February	1st to 10th	Day	13% 19% 31% 23% 12% 2	430
	11th to 20th	Day	15% 20% 28% 24% 10% 2	527
	21st to end	Day	17% 16% 31% 23% 11% 2	446
March	1st to 10th	Day	16% 23% 31% 21% 9%	540
	11th to 20th	Day	14% 21% 26% 24% 12% 3	540
	21st to end	Day	16% 24% 26% 23% 10% 1	594
April	1st to 10th	Day	16% 19% 25% 24% 14% 2	540
	11th to 20th	Day	14% 19% 29% 22% 13% 3	532
	21st to end	Day	13% 20% 25% 24% 15% 2	540
May	1st to 10th	Day	12% 18% 28% 24% 13% 4	543
	11th to 20th	Day	23% 15% 23% 20% 15% 5%	568
	21st to end	Day	18% 10% 22% 25% 18% 7%	617
June	1st to 10th	Day	11% 16% 24% 23% 18% 7%	570
	11th to 20th	Day	15% 17% 30% 23% 11% 4	570
	21st to end	Day	6% 11% 26% 33% 20% 5%	570
July	1st to 10th	Day	4 6% 34% 35% 17% 4	566
	11th to 20th	Day	3 10% 32% 36% 16% 3	564
	21st to end	Day	4 6% 28% 36% 20% 6%	619
August	1st to 10th	Day	6% 6% 28% 32% 21% 7%	567
	11th to 20th	Day	4 7% 30% 30% 22% 7%	557
	21st to end	Day	6% 9% 27% 30% 21% 7%	627
September	1st to 10th	Day	8% 9% 26% 32% 19% 6%	570
	11th to 20th	Day	9% 11% 25% 29% 20% 6%	570
	21st to end	Day	8% 11% 26% 29% 22% 4	570
October	1st to 10th	Day	13% 14% 23% 26% 18% 6%	570
	11th to 20th	Day	11% 16% 27% 27% 17% 3	570
	21st to end	Day	14% 16% 29% 24% 14% 4	406
November	1st to 10th	Day	17% 15% 26% 24% 16% 2	330
	11th to 20th	Day	14% 18% 25% 23% 16% 3	330
	21st to end	Day	11% 15% 23% 28% 18% 4	247
December	1st to 10th	Day	12% 17% 21% 21% 18% 10%	220
	11th to 20th	Day	23% 15% 25% 22% 12% 2	220
	21st to end	Day	20% 14% 23% 24% 15% 4	242
January	1st to 10th	Night	14% 15% 25% 24% 17% 5%	840
	11th to 20th	Night	7% 14% 25% 29% 19% 6%	840
	21st to end	Night	9% 10% 24% 31% 19% 6%	924
February	1st to 10th	Night	12% 14% 27% 27% 17% 3	840
	11th to 20th	Night	10% 13% 29% 28% 16% 3	824
	21st to end	Night	10% 13% 28% 33% 15% 2	692
March	1st to 10th	Night	9% 15% 31% 27% 14% 3	840
	11th to 20th	Night	13% 13% 25% 29% 17% 3	840
	21st to end	Night	12% 16% 26% 32% 13% 1	924
April	1st to 10th	Night	11% 10% 27% 33% 16% 3	840
	11th to 20th	Night	11% 15% 25% 28% 16% 5%	831
	21st to end	Night	12% 11% 23% 34% 17% 2	732
May	1st to 10th	Night	9% 15% 27% 29% 18% 2	607
	11th to 20th	Night	12% 13% 18% 29% 23% 5%	414
	21st to end	Night	13% 8% 18% 30% 25% 5%	455
June	1st to 10th	Night	11% 8% 16% 38% 23% 3	420
	11th to 20th	Night	11% 7% 26% 36% 18% 2	420
	21st to end	Night	5% 4 20% 43% 25% 2	420
July	1st to 10th	Night	4 3 17% 44% 27% 4	410
	11th to 20th	Night	2 3 19% 52% 21% 2	408
	21st to end	Night	3 1 17% 48% 27% 3	460
August	1st to 10th	Night	6% 3 12% 50% 26% 3	418
	11th to 20th	Night	3 3 14% 42% 34% 4	817
	21st to end	Night	5% 3 17% 42% 29% 3	924
September	1st to 10th	Night	5% 3 14% 42% 30% 5%	840
	11th to 20th	Night	7% 5% 15% 33% 30% 10%	840
	21st to end	Night	8% 4 18% 32% 28% 10%	840
October	1st to 10th	Night	11% 5% 21% 35% 22% 6%	840
	11th to 20th	Night	7% 10% 21% 33% 22% 7%	840
	21st to end	Night	11% 10% 21% 33% 18% 8%	912
November	1st to 10th	Night	16% 12% 19% 30% 21% 4	820
	11th to 20th	Night	14% 13% 27% 28% 16% 3	840
	21st to end	Night	10% 13% 23% 31% 17% 6%	840
December	1st to 10th	Night	10% 14% 23% 29% 19% 5%	840
	11th to 20th	Night	13% 13% 26% 28% 17% 4	840
	21st to end	Night	16% 18% 26% 27% 11% 2	924

Page generated at 2026-10-26 01:37:45. Version ac07

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