Gabriel Lake
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Gabriel Lake clear sky chart from 2005-11-06 to 2026-07-31.

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	17% 8% 3 8% 5% 4 5% 4 6% 7% 33%	138476
	Night	17% 9% 3 8% 5% 4 4 4 5% 7% 35%	134551
Transparency	Day	47% 7% 12% 21% 12% 2	141980
	Night	46% 7% 12% 21% 12% 2	139136
Seeing	Day	24% 17% 27% 19% 9% 3	17060
	Night	23% 15% 27% 24% 9% 1	26177

By Month

Percentage Cloud Cover NE (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	12% 12% 5% 17% 8% 4 5% 4 5% 6% 23%	4661
	11th to 20th	Day	14% 11% 5% 13% 7% 4 5% 4 5% 6% 26%	4650
	21st to end	Day	15% 9% 4 9% 5% 5% 4 3 4 7% 35%	5618
February	1st to 10th	Day	15% 10% 4 10% 5% 6% 6% 4 5% 7% 29%	1890
	11th to 20th	Day	14% 10% 4 9% 6% 5% 5% 4 6% 7% 31%	1985
	21st to end	Day	18% 9% 4 9% 6% 4 4 3 5% 6% 32%	1730
March	1st to 10th	Day	20% 10% 4 8% 5% 4 3 3 4 5% 34%	4576
	11th to 20th	Day	14% 9% 3 8% 6% 5% 4 4 5% 6% 37%	4993
	21st to end	Day	19% 8% 3 6% 5% 4 5% 4 6% 6% 34%	5979
April	1st to 10th	Day	19% 10% 3 8% 5% 4 5% 3 5% 6% 33%	2520
	11th to 20th	Day	17% 9% 3 7% 5% 4 5% 3 5% 7% 36%	2494
	21st to end	Day	18% 8% 3 7% 5% 4 5% 3 5% 6% 35%	2521
May	1st to 10th	Day	26% 8% 2 6% 4 4 4 4 5% 7% 29%	7873
	11th to 20th	Day	17% 9% 3 8% 5% 5% 5% 4 5% 6% 34%	8221
	21st to end	Day	23% 7% 2 6% 4 5% 6% 5% 7% 9% 27%	9060
June	1st to 10th	Day	16% 6% 2 7% 5% 6% 5% 5% 6% 9% 33%	2940
	11th to 20th	Day	17% 7% 2 7% 5% 5% 6% 4 7% 9% 31%	2940
	21st to end	Day	14% 7% 3 7% 4 5% 5% 4 7% 9% 35%	2940
July	1st to 10th	Day	10% 7% 3 8% 5% 5% 6% 5% 7% 9% 35%	6500
	11th to 20th	Day	11% 7% 2 8% 5% 5% 6% 5% 8% 10% 32%	6500
	21st to end	Day	14% 6% 2 6% 4 5% 5% 4 7% 8% 39%	7066
August	1st to 10th	Day	20% 7% 3 7% 4 5% 5% 4 6% 8% 30%	4342
	11th to 20th	Day	14% 7% 3 6% 4 5% 5% 4 7% 9% 36%	3886
	21st to end	Day	16% 5% 2 4 3 4 4 3 7% 10% 40%	4312
September	1st to 10th	Day	15% 7% 2 7% 4 4 5% 3 6% 6% 41%	2400
	11th to 20th	Day	13% 5% 2 5% 4 4 4 3 5% 8% 47%	2350
	21st to end	Day	19% 6% 2 7% 4 5% 5% 3 6% 6% 37%	2200
October	1st to 10th	Day	19% 6% 2 7% 4 4 4 3 4 8% 39%	2023
	11th to 20th	Day	16% 8% 3 6% 5% 4 5% 3 5% 7% 39%	2000
	21st to end	Day	22% 8% 2 7% 4 4 5% 4 6% 6% 32%	2065
November	1st to 10th	Day	14% 7% 2 7% 3 4 4 2 6% 7% 44%	1851
	11th to 20th	Day	16% 9% 3 7% 4 4 4 4 5% 6% 36%	1890
	21st to end	Day	18% 11% 3 7% 6% 4 4 3 6% 7% 31%	1706
December	1st to 10th	Day	17% 9% 5% 11% 7% 6% 5% 4 6% 6% 25%	2680
	11th to 20th	Day	21% 11% 4 7% 5% 4 4 3 5% 5% 32%	3066
	21st to end	Day	18% 12% 5% 11% 6% 4 5% 3 5% 6% 26%	4048
January	1st to 10th	Night	13% 12% 5% 15% 6% 4 5% 4 5% 6% 25%	8234
	11th to 20th	Night	12% 9% 5% 16% 8% 5% 5% 4 5% 6% 25%	8235
	21st to end	Night	14% 9% 3 7% 7% 6% 5% 4 5% 7% 33%	8544
February	1st to 10th	Night	15% 10% 4 7% 5% 4 5% 4 6% 7% 33%	2730
	11th to 20th	Night	14% 9% 4 9% 5% 5% 5% 5% 6% 7% 30%	2520
	21st to end	Night	17% 10% 3 7% 5% 4 4 4 6% 6% 33%	2076
March	1st to 10th	Night	19% 10% 4 6% 4 4 3 3 6% 6% 35%	5484
	11th to 20th	Night	13% 8% 4 7% 5% 5% 5% 4 5% 7% 37%	5183
	21st to end	Night	16% 10% 4 8% 6% 4 4 3 4 6% 35%	5195
April	1st to 10th	Night	19% 10% 3 8% 5% 5% 4 4 6% 6% 30%	2100
	11th to 20th	Night	18% 9% 3 7% 4 4 5% 4 5% 6% 35%	2075
	21st to end	Night	19% 9% 3 6% 5% 2 3 3 5% 6% 39%	2096
May	1st to 10th	Night	28% 8% 3 6% 4 4 4 3 5% 7% 29%	5080
	11th to 20th	Night	19% 9% 3 6% 4 4 4 3 6% 8% 34%	4639
	21st to end	Night	22% 9% 3 7% 5% 4 4 4 5% 6% 30%	5114
June	1st to 10th	Night	17% 6% 2 5% 4 4 4 4 5% 8% 41%	1680
	11th to 20th	Night	16% 7% 2 6% 4 4 3 3 5% 8% 41%	1680
	21st to end	Night	12% 5% 2 5% 4 4 5% 4 6% 9% 44%	1680
July	1st to 10th	Night	11% 8% 2 7% 5% 4 4 4 6% 8% 41%	3680
	11th to 20th	Night	14% 8% 3 7% 5% 4 4 4 6% 9% 34%	3680
	21st to end	Night	13% 6% 2 6% 4 4 5% 3 5% 8% 46%	4006
August	1st to 10th	Night	23% 7% 3 6% 4 5% 5% 4 5% 8% 31%	2804
	11th to 20th	Night	17% 7% 2 5% 4 4 4 3 5% 7% 41%	3129
	21st to end	Night	14% 4 2 4 4 3 4 4 5% 8% 48%	3586
September	1st to 10th	Night	15% 7% 1 4 4 3 4 4 6% 7% 45%	2000
	11th to 20th	Night	13% 5% 2 4 3 3 3 3 5% 7% 52%	2049
	21st to end	Night	17% 8% 2 7% 4 3 4 3 6% 6% 42%	2200
October	1st to 10th	Night	21% 7% 2 5% 3 3 4 3 5% 6% 41%	2373
	11th to 20th	Night	19% 7% 2 6% 3 3 3 3 4 6% 43%	2400
	21st to end	Night	21% 9% 3 6% 4 4 3 3 5% 7% 35%	2773
November	1st to 10th	Night	13% 7% 3 6% 3 4 4 3 5% 7% 44%	2667
	11th to 20th	Night	18% 8% 3 6% 4 4 4 3 6% 7% 37%	2730
	21st to end	Night	15% 10% 3 7% 5% 4 4 4 5% 8% 35%	2911
December	1st to 10th	Night	15% 11% 5% 10% 5% 4 4 4 6% 7% 30%	4720
	11th to 20th	Night	24% 10% 3 7% 4 4 4 3 4 5% 32%	5348
	21st to end	Night	20% 13% 5% 9% 5% 4 4 3 4 6% 27%	7150

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	55% 9% 10% 19% 6% 1	4662
	11th to 20th	Day	54% 7% 9% 16% 11% 3	4680
	21st to end	Day	48% 6% 10% 22% 13%	5618
February	1st to 10th	Day	53% 6% 10% 18% 11% 1	1890
	11th to 20th	Day	50% 7% 9% 21% 12% 1	1994
	21st to end	Day	52% 5% 11% 21% 11% 1	1730
March	1st to 10th	Day	52% 5% 10% 17% 11% 5%	4579
	11th to 20th	Day	44% 7% 14% 25% 7% 4	4993
	21st to end	Day	47% 6% 8% 14% 20% 5%	5979
April	1st to 10th	Day	51% 5% 9% 20% 12% 3	2520
	11th to 20th	Day	47% 6% 12% 21% 13% 2	2494
	21st to end	Day	48% 6% 9% 20% 13% 4	2521
May	1st to 10th	Day	53% 6% 12% 17% 11% 1	7885
	11th to 20th	Day	49% 7% 11% 21% 12% 1	8225
	21st to end	Day	50% 8% 13% 19% 10% 1	9061
June	1st to 10th	Day	45% 7% 12% 21% 14%	2940
	11th to 20th	Day	47% 7% 14% 21% 10% 1	2940
	21st to end	Day	43% 7% 13% 25% 11% 1	2940
July	1st to 10th	Day	44% 8% 13% 22% 12% 1	6430
	11th to 20th	Day	41% 10% 15% 23% 10%	6425
	21st to end	Day	40% 7% 13% 23% 17% 1	6868
August	1st to 10th	Day	50% 7% 13% 20% 9% 1	4328
	11th to 20th	Day	41% 8% 15% 27% 8%	3923
	21st to end	Day	36% 7% 13% 33% 11% 1	4312
September	1st to 10th	Day	42% 7% 11% 23% 16% 1	2400
	11th to 20th	Day	36% 5% 10% 25% 22% 1	2350
	21st to end	Day	46% 6% 11% 19% 16% 2	2200
October	1st to 10th	Day	41% 6% 9% 23% 19% 2	3296
	11th to 20th	Day	38% 6% 9% 25% 15% 7%	3240
	21st to end	Day	34% 5% 17% 27% 15% 3	3316
November	1st to 10th	Day	40% 4 13% 24% 17% 2	1851
	11th to 20th	Day	46% 7% 10% 21% 13% 3	1890
	21st to end	Day	51% 6% 14% 23% 6% 1	1706
December	1st to 10th	Day	56% 8% 12% 17% 6% 1	2680
	11th to 20th	Day	52% 7% 12% 17% 11% 1	3066
	21st to end	Day	57% 6% 9% 16% 11% 1	4048
January	1st to 10th	Night	56% 7% 10% 17% 9% 1	8234
	11th to 20th	Night	54% 9% 11% 15% 9% 2	8280
	21st to end	Night	47% 7% 9% 19% 15% 2	8544
February	1st to 10th	Night	48% 6% 14% 21% 10% 1	2730
	11th to 20th	Night	48% 8% 12% 18% 12% 2	2522
	21st to end	Night	49% 6% 8% 23% 12% 2	2076
March	1st to 10th	Night	47% 5% 13% 18% 15% 2	5494
	11th to 20th	Night	43% 8% 17% 21% 8% 4	5184
	21st to end	Night	48% 7% 6% 18% 18% 2	5195
April	1st to 10th	Night	52% 6% 10% 18% 12% 2	2100
	11th to 20th	Night	48% 6% 10% 20% 16% 1	2075
	21st to end	Night	45% 6% 9% 21% 16% 3	2096
May	1st to 10th	Night	53% 6% 13% 15% 10% 2	5086
	11th to 20th	Night	47% 7% 13% 22% 10% 1	4640
	21st to end	Night	51% 8% 11% 21% 8% 1	5115
June	1st to 10th	Night	41% 6% 10% 26% 16% 1	1680
	11th to 20th	Night	40% 6% 17% 26% 10% 1	1680
	21st to end	Night	34% 8% 17% 26% 13% 1	1680
July	1st to 10th	Night	41% 8% 15% 19% 15% 2	3640
	11th to 20th	Night	45% 8% 13% 22% 11% 1	3632
	21st to end	Night	36% 6% 13% 28% 16% 1	3889
August	1st to 10th	Night	50% 8% 14% 20% 7% 1	2794
	11th to 20th	Night	41% 6% 15% 29% 9%	3158
	21st to end	Night	33% 7% 13% 34% 13% 1	3586
September	1st to 10th	Night	37% 8% 13% 26% 16% 1	2000
	11th to 20th	Night	32% 5% 11% 26% 24% 1	2049
	21st to end	Night	43% 5% 10% 23% 18% 1	2200
October	1st to 10th	Night	43% 7% 10% 22% 17% 1	3880
	11th to 20th	Night	34% 6% 12% 23% 20% 5%	3899
	21st to end	Night	35% 6% 16% 27% 15% 1	4472
November	1st to 10th	Night	39% 6% 11% 24% 18% 2	2667
	11th to 20th	Night	44% 6% 12% 21% 14% 3	2730
	21st to end	Night	44% 7% 16% 24% 9%	2911
December	1st to 10th	Night	49% 8% 14% 23% 5%	4720
	11th to 20th	Night	52% 6% 12% 17% 12% 1	5348
	21st to end	Night	55% 7% 10% 15% 12% 2	7150

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	30% 31% 27% 10% 2	220
	11th to 20th	Day	45% 24% 21% 8% 1	220
	21st to end	Day	34% 27% 28% 8% 2 1	333
February	1st to 10th	Day	34% 28% 29% 8% 1	330
	11th to 20th	Day	35% 28% 28% 7% 1	473
	21st to end	Day	32% 26% 29% 11% 2	446
March	1st to 10th	Day	32% 22% 27% 15% 3	540
	11th to 20th	Day	33% 24% 26% 13% 3 1	540
	21st to end	Day	30% 28% 26% 9% 4 2	594
April	1st to 10th	Day	34% 24% 25% 12% 5% 1	540
	11th to 20th	Day	31% 23% 25% 12% 7% 2	532
	21st to end	Day	30% 18% 34% 13% 4 2	540
May	1st to 10th	Day	34% 20% 25% 12% 7% 2	543
	11th to 20th	Day	22% 19% 31% 18% 8% 3	567
	21st to end	Day	23% 12% 28% 21% 13% 3	617
June	1st to 10th	Day	19% 14% 29% 24% 11% 2	570
	11th to 20th	Day	23% 14% 26% 24% 12% 1	570
	21st to end	Day	17% 13% 32% 26% 10% 2	570
July	1st to 10th	Day	12% 10% 27% 31% 16% 5%	565
	11th to 20th	Day	12% 7% 30% 30% 18% 3	564
	21st to end	Day	17% 9% 32% 28% 11% 4	616
August	1st to 10th	Day	13% 10% 26% 26% 20% 6%	526
	11th to 20th	Day	16% 8% 24% 27% 18% 7%	519
	21st to end	Day	13% 11% 30% 24% 15% 7%	583
September	1st to 10th	Day	19% 11% 24% 22% 16% 8%	530
	11th to 20th	Day	14% 8% 23% 26% 16% 13%	530
	21st to end	Day	22% 10% 27% 23% 14% 4	530
October	1st to 10th	Day	25% 11% 23% 20% 15% 5%	530
	11th to 20th	Day	22% 18% 27% 21% 10% 2	530
	21st to end	Day	29% 15% 27% 20% 9%	509
November	1st to 10th	Day	22% 20% 23% 23% 10% 3	425
	11th to 20th	Day	27% 24% 25% 18% 6% 1	430
	21st to end	Day	31% 23% 29% 13% 3 1	246
December	1st to 10th	Day	31% 25% 27% 11% 4 1	220
	11th to 20th	Day	39% 24% 25% 9% 3	220
	21st to end	Day	29% 24% 27% 14% 5%	242
January	1st to 10th	Night	25% 25% 31% 16% 3	840
	11th to 20th	Night	29% 20% 30% 19% 2	840
	21st to end	Night	22% 26% 34% 17% 2	924
February	1st to 10th	Night	26% 20% 33% 19% 1	840
	11th to 20th	Night	28% 25% 32% 14% 1	823
	21st to end	Night	28% 23% 30% 16% 2	692
March	1st to 10th	Night	28% 20% 33% 15% 3	840
	11th to 20th	Night	27% 22% 28% 20% 3	840
	21st to end	Night	24% 22% 33% 16% 5%	924
April	1st to 10th	Night	28% 21% 31% 18% 3	840
	11th to 20th	Night	25% 18% 31% 20% 7%	831
	21st to end	Night	25% 19% 28% 23% 6%	836
May	1st to 10th	Night	30% 15% 26% 23% 5% 1	567
	11th to 20th	Night	22% 10% 29% 29% 9%	414
	21st to end	Night	20% 7% 23% 35% 14%	455
June	1st to 10th	Night	17% 8% 25% 34% 16%	420
	11th to 20th	Night	19% 7% 26% 33% 14%	420
	21st to end	Night	13% 4 27% 43% 14%	420
July	1st to 10th	Night	15% 5% 17% 41% 20% 2	410
	11th to 20th	Night	13% 4 19% 45% 18% 1	408
	21st to end	Night	14% 5% 19% 43% 19% 1	458
August	1st to 10th	Night	14% 2 20% 37% 25% 2	525
	11th to 20th	Night	17% 3 14% 39% 23% 3	746
	21st to end	Night	16% 5% 19% 35% 23% 2	880
September	1st to 10th	Night	18% 6% 24% 30% 20% 2	800
	11th to 20th	Night	15% 6% 20% 31% 23% 5%	800
	21st to end	Night	20% 8% 22% 30% 17% 2	800
October	1st to 10th	Night	24% 9% 23% 24% 18% 2	800
	11th to 20th	Night	24% 12% 27% 28% 8% 1	800
	21st to end	Night	27% 15% 29% 22% 6%	880
November	1st to 10th	Night	19% 16% 29% 26% 9% 1	820
	11th to 20th	Night	27% 19% 25% 22% 6% 1	840
	21st to end	Night	23% 20% 30% 22% 5% 1	840
December	1st to 10th	Night	27% 22% 28% 18% 5%	840
	11th to 20th	Night	29% 22% 28% 19% 3	840
	21st to end	Night	29% 21% 30% 17% 3	924

Page generated at 2026-07-28 03:25:20. Version ac07

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