Abraham Lake
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Abraham Lake clear sky chart from 2005-11-06 to 2026-09-14.

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	5% 8% 3 9% 6% 6% 6% 5% 8% 9% 35%	155229
	Night	3 7% 3 10% 6% 6% 7% 6% 9% 10% 34%	144550
Transparency	Day	40% 10% 18% 22% 9% 1	154935
	Night	39% 11% 20% 20% 8% 1	144427
Seeing	Day	17% 21% 33% 20% 7% 1	18299
	Night	11% 18% 39% 24% 9% 1	26495

By Month

Percentage Cloud Cover NW (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	3 2 10% 10% 11% 8% 6% 11% 11% 28%	4125
	11th to 20th	Day	2 3 7% 7% 7% 6% 6% 8% 10% 43%	4399
	21st to end	Day	4 3 10% 7% 6% 6% 6% 10% 13% 36%	5186
February	1st to 10th	Day	1 6% 4 10% 9% 9% 10% 7% 11% 10% 25%	1680
	11th to 20th	Day	1 8% 3 11% 8% 8% 8% 7% 8% 9% 29%	1744
	21st to end	Day	1 5% 5% 11% 11% 9% 9% 7% 9% 10% 23%	1730
March	1st to 10th	Day	1 6% 4 14% 10% 8% 6% 5% 7% 8% 31%	4618
	11th to 20th	Day	2 7% 3 11% 8% 7% 8% 6% 8% 9% 30%	4839
	21st to end	Day	2 13% 7% 20% 8% 6% 6% 5% 8% 7% 18%	5965
April	1st to 10th	Day	3 13% 6% 14% 9% 9% 8% 6% 7% 8% 17%	2520
	11th to 20th	Day	3 13% 6% 15% 10% 6% 7% 5% 7% 8% 20%	2679
	21st to end	Day	5% 15% 6% 14% 7% 6% 6% 5% 6% 7% 22%	2790
May	1st to 10th	Day	4 14% 4 8% 5% 5% 5% 4 7% 10% 36%	8195
	11th to 20th	Day	6% 11% 4 11% 7% 7% 7% 5% 9% 9% 25%	8673
	21st to end	Day	10% 11% 4 9% 6% 5% 6% 5% 6% 9% 31%	9649
June	1st to 10th	Day	14% 12% 3 10% 6% 6% 6% 5% 7% 8% 23%	3155
	11th to 20th	Day	18% 12% 3 9% 6% 5% 6% 4 7% 7% 22%	3360
	21st to end	Day	11% 9% 4 8% 7% 5% 7% 4 7% 8% 29%	3360
July	1st to 10th	Day	4 4 2 5% 4 4 5% 4 7% 9% 53%	9402
	11th to 20th	Day	7% 4 2 5% 4 4 5% 5% 7% 9% 48%	8820
	21st to end	Day	6% 5% 2 6% 4 4 5% 4 7% 9% 48%	9116
August	1st to 10th	Day	8% 7% 2 6% 4 5% 5% 4 7% 8% 42%	6441
	11th to 20th	Day	9% 5% 2 5% 4 5% 6% 5% 8% 10% 40%	6280
	21st to end	Day	8% 5% 3 6% 5% 5% 5% 5% 8% 9% 42%	6548
September	1st to 10th	Day	10% 10% 3 7% 4 4 5% 4 5% 8% 39%	2520
	11th to 20th	Day	8% 10% 3 8% 6% 4 5% 4 6% 8% 38%	2316
	21st to end	Day	8% 9% 4 9% 6% 7% 5% 5% 6% 7% 33%	2200
October	1st to 10th	Day	4 8% 3 7% 6% 6% 7% 6% 8% 9% 37%	3436
	11th to 20th	Day	4 8% 4 9% 6% 6% 7% 6% 8% 11% 33%	2932
	21st to end	Day	1 8% 4 8% 6% 7% 6% 5% 9% 9% 37%	3200
November	1st to 10th	Day	1 7% 4 12% 8% 7% 8% 6% 9% 11% 27%	1764
	11th to 20th	Day	1 6% 3 9% 7% 7% 8% 6% 11% 11% 31%	1470
	21st to end	Day	1 7% 4 10% 8% 9% 6% 6% 8% 10% 31%	1470
December	1st to 10th	Day	1 3 2 9% 8% 6% 7% 7% 11% 12% 34%	2360
	11th to 20th	Day	5% 3 10% 7% 9% 9% 7% 11% 11% 28%	2712
	21st to end	Day	4 3 9% 6% 7% 7% 7% 12% 11% 35%	3575
January	1st to 10th	Night	3 4 15% 10% 9% 8% 6% 10% 11% 23%	8768
	11th to 20th	Night	3 2 8% 7% 7% 7% 6% 10% 10% 40%	8558
	21st to end	Night	4 3 10% 6% 7% 8% 6% 9% 10% 36%	8994
February	1st to 10th	Night	1 7% 3 10% 9% 9% 8% 7% 10% 11% 24%	2940
	11th to 20th	Night	1 6% 4 12% 6% 8% 8% 5% 10% 11% 29%	2757
	21st to end	Night	5% 4 10% 11% 8% 8% 7% 9% 10% 27%	2076
March	1st to 10th	Night	1 7% 5% 12% 8% 8% 9% 6% 8% 9% 27%	5496
	11th to 20th	Night	2 6% 3 11% 7% 6% 8% 7% 9% 10% 31%	5367
	21st to end	Night	1 13% 8% 17% 7% 5% 6% 5% 8% 9% 21%	5238
April	1st to 10th	Night	2 11% 5% 12% 9% 7% 6% 6% 9% 9% 25%	2100
	11th to 20th	Night	3 11% 5% 13% 7% 4 5% 5% 7% 9% 31%	1892
	21st to end	Night	3 12% 4 11% 6% 5% 5% 5% 6% 7% 34%	1827
May	1st to 10th	Night	5% 15% 4 9% 4 4 4 3 6% 9% 38%	4724
	11th to 20th	Night	6% 14% 4 10% 5% 5% 6% 5% 8% 9% 27%	4187
	21st to end	Night	7% 8% 3 7% 5% 5% 5% 5% 9% 11% 36%	4522
June	1st to 10th	Night	13% 11% 3 7% 4 5% 5% 4 6% 8% 33%	1460
	11th to 20th	Night	14% 10% 4 9% 7% 6% 6% 5% 6% 7% 26%	1260
	21st to end	Night	8% 7% 2 6% 5% 5% 5% 5% 7% 10% 41%	1260
July	1st to 10th	Night	4 5% 2 6% 4 4 5% 4 8% 9% 49%	3540
	11th to 20th	Night	6% 5% 1 4 3 3 4 3 6% 8% 56%	4140
	21st to end	Night	6% 5% 2 4 3 4 4 5% 8% 9% 50%	4949
August	1st to 10th	Night	10% 9% 2 6% 3 3 4 4 6% 8% 45%	3709
	11th to 20th	Night	8% 7% 2 5% 4 3 4 4 8% 11% 43%	3767
	21st to end	Night	7% 6% 2 6% 4 5% 5% 5% 7% 9% 43%	4599
September	1st to 10th	Night	8% 8% 2 5% 4 4 6% 4 6% 9% 44%	2100
	11th to 20th	Night	8% 10% 3 7% 5% 4 5% 4 5% 8% 41%	2150
	21st to end	Night	5% 8% 3 7% 4 5% 5% 5% 7% 9% 41%	2200
October	1st to 10th	Night	4 7% 4 8% 4 5% 5% 5% 8% 12% 38%	3759
	11th to 20th	Night	3 8% 3 9% 5% 6% 7% 5% 8% 10% 37%	4216
	21st to end	Night	2 7% 4 11% 7% 7% 6% 5% 7% 9% 36%	4600
November	1st to 10th	Night	1 9% 5% 11% 9% 8% 8% 6% 9% 10% 25%	2732
	11th to 20th	Night	1 5% 3 10% 8% 8% 10% 7% 9% 11% 28%	3150
	21st to end	Night	1 7% 4 11% 9% 7% 8% 6% 9% 9% 29%	3150
December	1st to 10th	Night	1 5% 2 9% 6% 6% 8% 8% 14% 11% 30%	5040
	11th to 20th	Night	4 4 12% 8% 9% 9% 8% 12% 12% 23%	5700
	21st to end	Night	1 5% 3 10% 8% 8% 8% 7% 11% 12% 28%	7623

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	41% 11% 22% 16% 9% 1	4125
	11th to 20th	Day	33% 11% 19% 21% 13% 3	4421
	21st to end	Day	30% 16% 25% 21% 7%	5187
February	1st to 10th	Day	43% 12% 17% 14% 11% 3	1680
	11th to 20th	Day	44% 12% 14% 20% 10% 1	1752
	21st to end	Day	50% 12% 13% 15% 8% 1	1730
March	1st to 10th	Day	40% 13% 17% 16% 14%	4618
	11th to 20th	Day	36% 14% 19% 20% 10%	4840
	21st to end	Day	57% 10% 13% 12% 8%	5965
April	1st to 10th	Day	55% 15% 15% 11% 3	2520
	11th to 20th	Day	56% 11% 14% 15% 4	2679
	21st to end	Day	58% 10% 13% 15% 3	2790
May	1st to 10th	Day	43% 6% 25% 20% 6%	8195
	11th to 20th	Day	48% 10% 16% 21% 6%	8677
	21st to end	Day	45% 12% 22% 18% 3	9650
June	1st to 10th	Day	55% 10% 13% 15% 6% 1	3155
	11th to 20th	Day	57% 9% 12% 15% 7%	3360
	21st to end	Day	49% 9% 17% 17% 8% 1	3360
July	1st to 10th	Day	26% 6% 14% 33% 19% 2	9323
	11th to 20th	Day	31% 7% 14% 26% 19% 4	8739
	21st to end	Day	30% 8% 18% 28% 15% 1	8919
August	1st to 10th	Day	35% 8% 15% 32% 10%	6424
	11th to 20th	Day	34% 10% 20% 31% 5%	6322
	21st to end	Day	35% 8% 21% 27% 8% 1	6547
September	1st to 10th	Day	40% 8% 19% 23% 9% 1	2520
	11th to 20th	Day	40% 8% 14% 26% 10% 1	2316
	21st to end	Day	43% 11% 17% 19% 9% 1	2200
October	1st to 10th	Day	39% 9% 24% 22% 6%	3436
	11th to 20th	Day	40% 10% 21% 23% 6% 1	2932
	21st to end	Day	35% 11% 25% 24% 5%	3200
November	1st to 10th	Day	44% 14% 19% 15% 7% 1	1764
	11th to 20th	Day	36% 13% 26% 17% 7%	1470
	21st to end	Day	40% 12% 20% 20% 5% 3	1470
December	1st to 10th	Day	39% 19% 25% 11% 6%	2360
	11th to 20th	Day	39% 13% 23% 18% 5% 1	2714
	21st to end	Day	33% 13% 19% 23% 12% 1	3575
January	1st to 10th	Night	46% 14% 19% 14% 7% 1	8769
	11th to 20th	Night	34% 13% 20% 15% 14% 3	8598
	21st to end	Night	35% 14% 26% 19% 5% 1	8994
February	1st to 10th	Night	47% 12% 13% 14% 11% 2	2940
	11th to 20th	Night	43% 12% 16% 18% 11%	2759
	21st to end	Night	44% 11% 14% 21% 9% 1	2076
March	1st to 10th	Night	42% 13% 17% 17% 11%	5496
	11th to 20th	Night	37% 14% 18% 22% 9%	5367
	21st to end	Night	53% 9% 12% 17% 8%	5238
April	1st to 10th	Night	46% 15% 16% 17% 6%	2100
	11th to 20th	Night	47% 9% 20% 16% 8%	1892
	21st to end	Night	46% 11% 17% 20% 5% 1	1827
May	1st to 10th	Night	44% 5% 23% 25% 2 1	4721
	11th to 20th	Night	47% 11% 16% 22% 4	4187
	21st to end	Night	35% 14% 26% 22% 4	4526
June	1st to 10th	Night	47% 8% 15% 21% 7% 1	1460
	11th to 20th	Night	52% 9% 16% 17% 6%	1260
	21st to end	Night	34% 9% 25% 25% 7%	1260
July	1st to 10th	Night	28% 7% 19% 31% 14%	3510
	11th to 20th	Night	26% 6% 18% 31% 18% 2	4098
	21st to end	Night	28% 7% 22% 28% 14%	4841
August	1st to 10th	Night	35% 8% 19% 34% 5%	3701
	11th to 20th	Night	31% 9% 30% 26% 4	3791
	21st to end	Night	34% 9% 26% 26% 5%	4599
September	1st to 10th	Night	34% 10% 21% 26% 9% 1	2100
	11th to 20th	Night	39% 8% 17% 24% 11% 1	2150
	21st to end	Night	34% 11% 22% 23% 9%	2200
October	1st to 10th	Night	36% 11% 24% 21% 8%	3759
	11th to 20th	Night	38% 10% 23% 23% 7%	4216
	21st to end	Night	40% 11% 21% 23% 5%	4600
November	1st to 10th	Night	47% 15% 15% 15% 7% 1	2732
	11th to 20th	Night	39% 16% 20% 16% 8% 1	3150
	21st to end	Night	43% 14% 18% 17% 6% 3	3150
December	1st to 10th	Night	44% 16% 19% 14% 7% 1	5040
	11th to 20th	Night	45% 15% 20% 14% 6%	5697
	21st to end	Night	39% 12% 21% 20% 7% 1	7623

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	14% 19% 36% 21% 9% 1	220
	11th to 20th	Day	15% 15% 45% 18% 4 2	220
	21st to end	Day	10% 32% 41% 10% 5% 1	242
February	1st to 10th	Day	19% 21% 40% 15% 5% 2	220
	11th to 20th	Day	12% 20% 41% 22% 5%	295
	21st to end	Day	19% 24% 36% 15% 6% 1	446
March	1st to 10th	Day	17% 26% 32% 16% 6% 2	540
	11th to 20th	Day	17% 26% 32% 20% 4 1	540
	21st to end	Day	18% 25% 31% 18% 5% 2	594
April	1st to 10th	Day	20% 25% 32% 17% 5% 1	540
	11th to 20th	Day	13% 27% 34% 18% 7% 2	532
	21st to end	Day	19% 23% 29% 20% 9% 1	540
May	1st to 10th	Day	18% 19% 37% 20% 6% 1	543
	11th to 20th	Day	16% 13% 31% 27% 12% 2	743
	21st to end	Day	23% 16% 29% 21% 10% 2	844
June	1st to 10th	Day	22% 22% 31% 19% 5% 1	785
	11th to 20th	Day	24% 21% 31% 17% 6% 1	990
	21st to end	Day	17% 17% 30% 23% 10% 2	990
July	1st to 10th	Day	14% 18% 34% 25% 8% 2	971
	11th to 20th	Day	17% 14% 36% 21% 11% 1	768
	21st to end	Day	12% 18% 34% 22% 11% 3	692
August	1st to 10th	Day	15% 16% 32% 25% 10% 2	567
	11th to 20th	Day	12% 22% 37% 21% 7% 2	557
	21st to end	Day	16% 22% 33% 22% 7% 2	627
September	1st to 10th	Day	18% 24% 28% 23% 6% 1	570
	11th to 20th	Day	18% 18% 37% 20% 6% 1	543
	21st to end	Day	22% 29% 29% 14% 5% 1	530
October	1st to 10th	Day	21% 24% 29% 18% 5% 2	524
	11th to 20th	Day	20% 23% 34% 18% 5%	330
	21st to end	Day	21% 23% 37% 14% 4 1	363
November	1st to 10th	Day	16% 27% 39% 12% 4 1	311
	11th to 20th	Day	21% 27% 37% 9% 5%	220
	21st to end	Day	15% 26% 30% 19% 5% 5%	220
December	1st to 10th	Day	12% 26% 38% 16% 5% 4	220
	11th to 20th	Day	13% 26% 39% 18% 3	220
	21st to end	Day	13% 17% 43% 19% 6% 1	242
January	1st to 10th	Night	10% 23% 48% 15% 4	1050
	11th to 20th	Night	9% 26% 44% 16% 4 1	971
	21st to end	Night	7% 29% 44% 15% 5%	924
February	1st to 10th	Night	10% 22% 38% 21% 8% 1	840
	11th to 20th	Night	7% 19% 44% 24% 6%	824
	21st to end	Night	9% 15% 40% 23% 12% 1	692
March	1st to 10th	Night	7% 21% 41% 23% 8% 1	840
	11th to 20th	Night	7% 18% 45% 22% 7% 1	840
	21st to end	Night	8% 16% 37% 28% 10% 1	924
April	1st to 10th	Night	9% 15% 36% 29% 10% 1	840
	11th to 20th	Night	10% 13% 43% 23% 10%	644
	21st to end	Night	12% 13% 37% 30% 8% 1	567
May	1st to 10th	Night	13% 10% 31% 33% 11% 1	420
	11th to 20th	Night	13% 5% 29% 36% 16%	414
	21st to end	Night	19% 10% 28% 31% 12%	455
June	1st to 10th	Night	19% 9% 35% 26% 9% 1	420
	11th to 20th	Night	19% 10% 32% 28% 10%	420
	21st to end	Night	13% 9% 30% 31% 16% 1	420
July	1st to 10th	Night	12% 6% 34% 34% 14%	410
	11th to 20th	Night	12% 9% 31% 37% 11%	408
	21st to end	Night	6% 6% 27% 43% 17% 1	460
August	1st to 10th	Night	14% 6% 20% 36% 23% 2	418
	11th to 20th	Night	12% 6% 27% 36% 19% 1	454
	21st to end	Night	12% 10% 31% 35% 11% 1	701
September	1st to 10th	Night	14% 12% 31% 30% 12% 2	840
	11th to 20th	Night	13% 9% 31% 32% 12% 2	812
	21st to end	Night	18% 20% 32% 20% 10% 1	800
October	1st to 10th	Night	13% 15% 36% 27% 10%	800
	11th to 20th	Night	16% 16% 41% 21% 6%	800
	21st to end	Night	13% 21% 41% 20% 4	880
November	1st to 10th	Night	11% 25% 44% 14% 5%	852
	11th to 20th	Night	13% 25% 46% 13% 3	1050
	21st to end	Night	10% 24% 42% 17% 6% 1	1050
December	1st to 10th	Night	9% 26% 39% 19% 6%	1050
	11th to 20th	Night	9% 24% 44% 17% 6% 1	1050
	21st to end	Night	5% 23% 47% 18% 6% 1	1155

Page generated at 2026-09-11 02:11:57. Version ac07

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