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 2025-03-27.

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% 5% 5% 4 6% 7% 33%	108972
	Night	17% 9% 3 8% 5% 4 4 4 5% 7% 35%	110361
Transparency	Day	47% 7% 12% 21% 12% 2	112522
	Night	46% 7% 12% 21% 13% 1	114975
Seeing	Day	24% 17% 27% 19% 10% 3	15271
	Night	23% 15% 27% 24% 9% 1	24583

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	11% 10% 5% 19% 8% 4 4 4 4 6% 25%	3597
	11th to 20th	Day	14% 12% 5% 15% 7% 5% 5% 4 6% 6% 23%	3570
	21st to end	Day	18% 11% 5% 9% 5% 5% 4 3 3 6% 33%	4346
February	1st to 10th	Day	16% 11% 4 10% 5% 6% 6% 4 5% 7% 27%	1800
	11th to 20th	Day	14% 10% 4 8% 6% 5% 5% 4 6% 7% 32%	1888
	21st to end	Day	19% 9% 4 9% 6% 4 4 3 5% 6% 31%	1650
March	1st to 10th	Day	23% 12% 3 8% 5% 4 3 2 3 5% 32%	3216
	11th to 20th	Day	10% 11% 4 9% 6% 5% 5% 4 5% 7% 34%	3521
	21st to end	Day	21% 9% 3 6% 4 4 4 3 5% 6% 35%	4157
April	1st to 10th	Day	18% 10% 3 8% 5% 4 5% 3 5% 6% 34%	2280
	11th to 20th	Day	17% 9% 3 7% 5% 4 5% 3 5% 6% 36%	2254
	21st to end	Day	18% 9% 3 7% 5% 4 5% 3 5% 6% 34%	2281
May	1st to 10th	Day	27% 8% 2 6% 5% 3 4 3 4 7% 30%	4230
	11th to 20th	Day	20% 9% 2 8% 6% 5% 5% 4 5% 6% 28%	4398
	21st to end	Day	13% 6% 2 5% 4 5% 6% 5% 7% 10% 39%	4837
June	1st to 10th	Day	16% 6% 2 7% 5% 6% 5% 5% 7% 9% 32%	2660
	11th to 20th	Day	17% 7% 2 8% 5% 5% 6% 5% 7% 9% 31%	2660
	21st to end	Day	14% 7% 3 7% 5% 5% 5% 4 7% 10% 34%	2660
July	1st to 10th	Day	10% 7% 3 8% 5% 5% 6% 5% 7% 9% 34%	4440
	11th to 20th	Day	10% 6% 2 7% 5% 5% 6% 5% 8% 11% 36%	4440
	21st to end	Day	14% 8% 3 7% 5% 6% 6% 4 7% 7% 32%	4814
August	1st to 10th	Day	21% 7% 3 7% 4 5% 5% 5% 6% 8% 29%	4209
	11th to 20th	Day	14% 7% 3 6% 4 5% 5% 4 7% 9% 35%	3765
	21st to end	Day	16% 5% 2 5% 3 4 4 4 7% 10% 40%	4180
September	1st to 10th	Day	16% 7% 2 6% 4 4 5% 3 6% 6% 40%	2280
	11th to 20th	Day	14% 5% 2 5% 4 4 4 3 5% 8% 46%	2233
	21st to end	Day	19% 6% 2 6% 4 5% 5% 3 5% 6% 38%	2090
October	1st to 10th	Day	20% 7% 2 7% 4 4 4 3 4 8% 37%	1922
	11th to 20th	Day	16% 8% 3 6% 5% 4 5% 3 5% 7% 39%	1900
	21st to end	Day	23% 8% 2 6% 4 4 5% 4 6% 6% 31%	1962
November	1st to 10th	Day	14% 7% 2 6% 3 4 4 2 5% 7% 45%	1761
	11th to 20th	Day	17% 9% 3 7% 4 4 4 4 5% 6% 37%	1800
	21st to end	Day	18% 11% 3 6% 6% 4 4 3 6% 7% 32%	1625
December	1st to 10th	Day	17% 9% 5% 11% 7% 6% 5% 4 6% 6% 24%	2600
	11th to 20th	Day	22% 11% 4 7% 5% 4 3 3 4 5% 32%	2986
	21st to end	Day	18% 12% 5% 10% 6% 4 5% 3 5% 6% 26%	3960
January	1st to 10th	Night	12% 9% 5% 16% 6% 4 4 4 5% 7% 28%	6349
	11th to 20th	Night	12% 9% 5% 16% 8% 6% 5% 4 5% 7% 25%	6315
	21st to end	Night	16% 10% 3 8% 6% 5% 5% 4 5% 6% 31%	6605
February	1st to 10th	Night	16% 10% 4 7% 5% 4 5% 4 6% 7% 32%	2600
	11th to 20th	Night	14% 9% 4 8% 5% 5% 5% 6% 7% 8% 30%	2397
	21st to end	Night	18% 10% 3 7% 5% 4 4 4 6% 6% 33%	1980
March	1st to 10th	Night	22% 13% 3 6% 4 4 3 3 5% 5% 32%	3844
	11th to 20th	Night	11% 9% 4 7% 5% 6% 5% 5% 6% 7% 34%	3655
	21st to end	Night	15% 10% 4 8% 5% 4 4 3 4 6% 37%	3614
April	1st to 10th	Night	17% 10% 3 8% 6% 5% 4 4 6% 6% 31%	1900
	11th to 20th	Night	18% 9% 3 7% 4 4 5% 3 5% 6% 36%	1875
	21st to end	Night	18% 9% 3 6% 4 2 3 3 6% 5% 39%	1896
May	1st to 10th	Night	28% 8% 3 6% 3 3 3 3 5% 6% 32%	2738
	11th to 20th	Night	21% 10% 3 7% 5% 3 4 3 6% 7% 32%	2495
	21st to end	Night	14% 7% 3 7% 5% 5% 5% 4 6% 9% 37%	2738
June	1st to 10th	Night	17% 6% 2 5% 5% 4 4 4 6% 8% 40%	1520
	11th to 20th	Night	15% 6% 2 6% 4 4 3 3 5% 9% 43%	1520
	21st to end	Night	11% 5% 2 5% 4 4 5% 4 6% 9% 45%	1520
July	1st to 10th	Night	11% 7% 2 6% 5% 4 5% 4 7% 8% 40%	2520
	11th to 20th	Night	13% 7% 2 6% 4 4 4 4 7% 9% 39%	2520
	21st to end	Night	16% 7% 2 6% 5% 4 5% 4 6% 7% 38%	2739
August	1st to 10th	Night	23% 7% 3 6% 4 5% 5% 4 5% 8% 31%	2717
	11th to 20th	Night	18% 7% 2 5% 4 4 4 3 5% 7% 41%	3031
	21st to end	Night	14% 4 2 4 4 3 4 4 5% 8% 48%	3476
September	1st to 10th	Night	15% 7% 1 4 4 4 4 4 6% 7% 44%	1900
	11th to 20th	Night	14% 5% 2 4 3 3 3 3 5% 7% 52%	1946
	21st to end	Night	17% 8% 2 7% 3 3 4 2 5% 5% 42%	2090
October	1st to 10th	Night	21% 7% 2 5% 3 3 4 4 5% 6% 39%	2254
	11th to 20th	Night	18% 7% 2 6% 3 3 3 3 4 6% 43%	2280
	21st to end	Night	21% 9% 2 6% 4 4 3 4 5% 7% 35%	2634
November	1st to 10th	Night	13% 7% 3 6% 3 4 4 3 5% 7% 44%	2537
	11th to 20th	Night	19% 8% 3 5% 4 4 4 3 6% 7% 38%	2600
	21st to end	Night	15% 10% 3 7% 4 4 4 4 5% 8% 36%	2772
December	1st to 10th	Night	15% 11% 5% 10% 5% 4 4 4 6% 7% 30%	4580
	11th to 20th	Night	25% 10% 3 7% 4 4 4 3 4 5% 32%	5208
	21st to end	Night	20% 13% 5% 9% 5% 4 4 3 4 6% 27%	6996

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	54% 10% 8% 21% 6% 1	3598
	11th to 20th	Day	58% 8% 9% 15% 8% 2	3600
	21st to end	Day	52% 6% 9% 22% 11% 1	4346
February	1st to 10th	Day	54% 7% 11% 17% 11% 1	1800
	11th to 20th	Day	48% 7% 10% 21% 13% 2	1897
	21st to end	Day	52% 5% 11% 21% 10% 1	1650
March	1st to 10th	Day	55% 4 10% 19% 10% 2	3219
	11th to 20th	Day	44% 8% 13% 25% 8% 2	3521
	21st to end	Day	48% 4 7% 17% 20% 4	4157
April	1st to 10th	Day	50% 5% 9% 21% 11% 3	2280
	11th to 20th	Day	47% 5% 10% 22% 13% 2	2254
	21st to end	Day	49% 6% 9% 20% 13% 4	2281
May	1st to 10th	Day	54% 5% 11% 17% 11% 2	4244
	11th to 20th	Day	54% 6% 12% 18% 8% 1	4402
	21st to end	Day	37% 9% 13% 26% 15% 1	4837
June	1st to 10th	Day	46% 7% 13% 20% 13%	2660
	11th to 20th	Day	47% 7% 13% 22% 10% 1	2660
	21st to end	Day	43% 8% 13% 25% 11%	2660
July	1st to 10th	Day	44% 8% 14% 22% 11% 1	4370
	11th to 20th	Day	38% 9% 17% 23% 12% 1	4365
	21st to end	Day	46% 8% 14% 19% 12% 1	4661
August	1st to 10th	Day	51% 8% 13% 19% 8%	4195
	11th to 20th	Day	41% 8% 16% 27% 7%	3802
	21st to end	Day	37% 7% 13% 32% 11% 1	4180
September	1st to 10th	Day	42% 7% 11% 23% 15% 1	2280
	11th to 20th	Day	37% 5% 10% 24% 23% 1	2233
	21st to end	Day	45% 5% 11% 20% 17% 2	2090
October	1st to 10th	Day	42% 6% 9% 22% 19% 2	3195
	11th to 20th	Day	38% 6% 9% 25% 16% 7%	3140
	21st to end	Day	33% 5% 17% 27% 14% 3	3213
November	1st to 10th	Day	40% 4 13% 24% 17% 2	1761
	11th to 20th	Day	45% 7% 10% 21% 14% 3	1800
	21st to end	Day	49% 6% 14% 23% 6% 1	1625
December	1st to 10th	Day	56% 8% 13% 17% 6% 1	2600
	11th to 20th	Day	52% 7% 13% 17% 11% 1	2986
	21st to end	Day	57% 6% 9% 15% 12% 1	3960
January	1st to 10th	Night	53% 7% 10% 19% 10% 1	6349
	11th to 20th	Night	53% 10% 13% 15% 8% 2	6360
	21st to end	Night	50% 7% 10% 16% 15% 2	6605
February	1st to 10th	Night	49% 7% 14% 21% 9% 1	2600
	11th to 20th	Night	47% 8% 12% 19% 12% 2	2399
	21st to end	Night	49% 6% 8% 23% 12% 2	1980
March	1st to 10th	Night	52% 5% 11% 19% 11% 1	3854
	11th to 20th	Night	44% 9% 14% 23% 9% 1	3656
	21st to end	Night	46% 8% 7% 19% 18% 3	3614
April	1st to 10th	Night	52% 6% 10% 19% 12% 2	1900
	11th to 20th	Night	47% 6% 10% 20% 16% 1	1875
	21st to end	Night	44% 6% 10% 21% 15% 3	1896
May	1st to 10th	Night	53% 5% 10% 20% 10% 2	2744
	11th to 20th	Night	52% 7% 14% 18% 9% 1	2496
	21st to end	Night	40% 10% 14% 24% 11% 1	2739
June	1st to 10th	Night	41% 6% 11% 26% 15% 1	1520
	11th to 20th	Night	39% 6% 18% 27% 10% 1	1520
	21st to end	Night	34% 9% 17% 27% 13% 1	1520
July	1st to 10th	Night	39% 9% 17% 19% 15% 2	2480
	11th to 20th	Night	39% 8% 14% 26% 12% 1	2472
	21st to end	Night	44% 6% 14% 21% 14% 1	2651
August	1st to 10th	Night	51% 8% 14% 19% 7% 1	2707
	11th to 20th	Night	41% 6% 15% 28% 9%	3060
	21st to end	Night	33% 7% 13% 34% 13%	3476
September	1st to 10th	Night	37% 8% 13% 25% 16% 1	1900
	11th to 20th	Night	33% 5% 11% 25% 24% 1	1946
	21st to end	Night	43% 5% 9% 23% 19% 1	2090
October	1st to 10th	Night	44% 7% 10% 22% 17% 1	3761
	11th to 20th	Night	33% 6% 12% 23% 20% 5%	3779
	21st to end	Night	35% 6% 16% 27% 15% 1	4333
November	1st to 10th	Night	39% 6% 11% 24% 19% 2	2537
	11th to 20th	Night	43% 5% 13% 22% 14% 3	2600
	21st to end	Night	43% 7% 16% 24% 9%	2772
December	1st to 10th	Night	49% 8% 14% 24% 5%	4580
	11th to 20th	Night	52% 6% 12% 17% 11% 1	5208
	21st to end	Night	55% 7% 10% 14% 12% 2	6996

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	31% 29% 28% 11% 2 1	200
	11th to 20th	Day	44% 23% 23% 9% 2 1	200
	21st to end	Day	31% 27% 30% 9% 3 1	303
February	1st to 10th	Day	36% 27% 29% 7% 1	300
	11th to 20th	Day	35% 28% 28% 7% 1	436
	21st to end	Day	32% 24% 29% 12% 2	414
March	1st to 10th	Day	31% 23% 27% 15% 3	500
	11th to 20th	Day	31% 25% 27% 13% 3 1	500
	21st to end	Day	30% 28% 26% 10% 5% 2	530
April	1st to 10th	Day	31% 23% 27% 12% 6% 1	460
	11th to 20th	Day	29% 23% 24% 13% 8% 3	452
	21st to end	Day	30% 18% 33% 13% 4 3	460
May	1st to 10th	Day	34% 17% 25% 14% 8% 3	463
	11th to 20th	Day	22% 18% 30% 19% 9% 3	487
	21st to end	Day	19% 11% 28% 24% 15% 3	529
June	1st to 10th	Day	19% 14% 30% 23% 11% 2	490
	11th to 20th	Day	19% 14% 26% 25% 14% 2	490
	21st to end	Day	17% 12% 32% 26% 11% 2	490
July	1st to 10th	Day	12% 9% 27% 29% 17% 6%	485
	11th to 20th	Day	12% 7% 29% 31% 19% 3	484
	21st to end	Day	15% 9% 33% 28% 11% 4	532
August	1st to 10th	Day	13% 10% 27% 24% 20% 5%	486
	11th to 20th	Day	16% 8% 25% 26% 17% 7%	479
	21st to end	Day	14% 11% 29% 24% 15% 8%	539
September	1st to 10th	Day	20% 11% 23% 21% 16% 8%	490
	11th to 20th	Day	14% 9% 22% 26% 15% 13%	490
	21st to end	Day	23% 10% 27% 23% 13% 4	490
October	1st to 10th	Day	26% 12% 23% 20% 14% 5%	490
	11th to 20th	Day	21% 18% 28% 22% 10% 2	490
	21st to end	Day	29% 14% 27% 20% 9%	472
November	1st to 10th	Day	21% 18% 24% 23% 11% 3	395
	11th to 20th	Day	27% 23% 26% 18% 6% 1	400
	21st to end	Day	28% 23% 30% 15% 3 1	225
December	1st to 10th	Day	31% 26% 27% 12% 4 1	200
	11th to 20th	Day	39% 24% 25% 10% 3	200
	21st to end	Day	28% 25% 27% 15% 5%	220
January	1st to 10th	Night	26% 25% 31% 16% 3	800
	11th to 20th	Night	29% 19% 30% 20% 2	800
	21st to end	Night	21% 25% 34% 17% 3	880
February	1st to 10th	Night	26% 20% 33% 19% 1	800
	11th to 20th	Night	28% 26% 31% 14% 1	783
	21st to end	Night	29% 23% 30% 16% 2	660
March	1st to 10th	Night	28% 20% 33% 15% 3	800
	11th to 20th	Night	26% 22% 29% 20% 4	800
	21st to end	Night	24% 22% 32% 17% 5%	863
April	1st to 10th	Night	25% 21% 31% 19% 3	760
	11th to 20th	Night	24% 18% 31% 20% 7%	751
	21st to end	Night	24% 18% 28% 23% 6%	756
May	1st to 10th	Night	30% 14% 26% 24% 6% 1	513
	11th to 20th	Night	21% 10% 30% 29% 9% 1	374
	21st to end	Night	18% 6% 22% 37% 16%	411
June	1st to 10th	Night	17% 8% 24% 34% 17%	380
	11th to 20th	Night	17% 7% 25% 35% 16%	380
	21st to end	Night	12% 4 28% 41% 15%	380
July	1st to 10th	Night	14% 5% 17% 41% 21% 2	370
	11th to 20th	Night	13% 3 20% 44% 19% 2	368
	21st to end	Night	14% 4 19% 42% 19% 1	416
August	1st to 10th	Night	14% 2 21% 37% 24% 2	498
	11th to 20th	Night	18% 3 14% 39% 23% 3	708
	21st to end	Night	16% 5% 18% 36% 23% 2	836
September	1st to 10th	Night	18% 6% 24% 30% 20% 3	760
	11th to 20th	Night	16% 6% 21% 29% 22% 5%	760
	21st to end	Night	20% 8% 23% 30% 16% 2	760
October	1st to 10th	Night	25% 10% 23% 24% 17% 2	760
	11th to 20th	Night	24% 11% 27% 28% 9% 1	760
	21st to end	Night	27% 15% 29% 22% 6%	836
November	1st to 10th	Night	18% 16% 29% 26% 10% 1	780
	11th to 20th	Night	26% 19% 26% 23% 7% 1	800
	21st to end	Night	21% 20% 31% 22% 5% 1	800
December	1st to 10th	Night	27% 22% 28% 19% 5%	800
	11th to 20th	Night	28% 21% 28% 19% 3	800
	21st to end	Night	28% 21% 31% 17% 3	880

Page generated at 2025-03-24 09:04:27. Version ac07

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