Battle River
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Battle River clear sky chart from 2005-11-06 to 2025-07-21.

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	10% 9% 3 9% 6% 5% 5% 4 6% 8% 35%	123981
	Night	8% 9% 4 10% 6% 6% 5% 5% 6% 8% 34%	123853
Transparency	Day	45% 8% 16% 22% 8% 1	123722
	Night	46% 7% 16% 21% 9% 1	123758
Seeing	Day	13% 9% 28% 30% 16% 5%	16508
	Night	12% 6% 30% 35% 15% 2	25563

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	6% 10% 5% 15% 10% 8% 6% 5% 7% 5% 24%	3179
	11th to 20th	Day	5% 8% 3 9% 8% 8% 9% 8% 8% 7% 27%	3159
	21st to end	Day	8% 13% 4 11% 7% 5% 5% 4 6% 7% 29%	3562
February	1st to 10th	Day	8% 14% 6% 14% 9% 6% 5% 4 5% 6% 23%	1665
	11th to 20th	Day	7% 13% 5% 13% 8% 6% 5% 5% 6% 8% 25%	1755
	21st to end	Day	4 13% 5% 11% 8% 6% 7% 6% 8% 9% 22%	1485
March	1st to 10th	Day	4 11% 5% 11% 7% 6% 6% 6% 8% 9% 28%	4586
	11th to 20th	Day	6% 10% 6% 17% 7% 5% 4 3 5% 9% 29%	4999
	21st to end	Day	9% 15% 5% 16% 8% 4 4 4 4 6% 25%	5486
April	1st to 10th	Day	7% 13% 4 9% 7% 4 5% 4 5% 7% 33%	2495
	11th to 20th	Day	11% 12% 5% 10% 5% 4 5% 4 5% 7% 31%	2570
	21st to end	Day	13% 12% 4 7% 4 4 5% 4 7% 8% 32%	2649
May	1st to 10th	Day	13% 9% 4 7% 5% 5% 5% 4 5% 6% 38%	6401
	11th to 20th	Day	16% 11% 3 9% 6% 5% 5% 4 7% 7% 26%	6734
	21st to end	Day	11% 7% 2 7% 5% 5% 5% 4 6% 7% 39%	7405
June	1st to 10th	Day	15% 6% 3 7% 6% 6% 6% 4 7% 8% 33%	3000
	11th to 20th	Day	19% 9% 3 10% 6% 6% 6% 5% 8% 7% 22%	3000
	21st to end	Day	12% 6% 2 5% 6% 5% 6% 6% 8% 9% 35%	3000
July	1st to 10th	Day	9% 5% 2 5% 4 5% 5% 5% 7% 8% 47%	4890
	11th to 20th	Day	10% 5% 3 6% 4 5% 5% 4 6% 8% 44%	4890
	21st to end	Day	7% 5% 2 5% 4 4 5% 4 7% 9% 49%	5139
August	1st to 10th	Day	13% 5% 2 6% 4 5% 5% 4 5% 7% 44%	4636
	11th to 20th	Day	8% 5% 2 6% 4 4 5% 4 7% 11% 45%	4028
	21st to end	Day	9% 5% 2 5% 4 5% 5% 4 6% 9% 46%	4521
September	1st to 10th	Day	10% 6% 3 6% 5% 5% 4 5% 5% 7% 44%	2370
	11th to 20th	Day	16% 8% 3 6% 4 3 4 3 5% 7% 42%	2160
	21st to end	Day	10% 7% 2 5% 4 4 5% 3 6% 8% 47%	2085
October	1st to 10th	Day	8% 10% 3 6% 5% 4 6% 4 5% 6% 42%	3170
	11th to 20th	Day	10% 8% 3 8% 5% 4 4 4 6% 10% 40%	3073
	21st to end	Day	7% 8% 4 8% 5% 5% 5% 4 6% 9% 40%	2916
November	1st to 10th	Day	12% 14% 5% 12% 7% 4 5% 4 5% 7% 26%	1568
	11th to 20th	Day	6% 13% 6% 15% 8% 5% 4 4 6% 7% 24%	1575
	21st to end	Day	5% 14% 6% 12% 6% 7% 5% 3 6% 9% 26%	1400
December	1st to 10th	Day	9% 12% 5% 11% 7% 7% 7% 6% 7% 7% 23%	2290
	11th to 20th	Day	8% 16% 5% 11% 7% 8% 6% 4 7% 7% 20%	2642
	21st to end	Day	3 8% 4 12% 8% 6% 5% 3 5% 8% 37%	3498
January	1st to 10th	Night	4 8% 4 14% 9% 10% 8% 7% 8% 7% 20%	6766
	11th to 20th	Night	3 9% 4 10% 9% 7% 7% 6% 6% 8% 30%	6739
	21st to end	Night	7% 11% 5% 10% 6% 5% 5% 4 6% 7% 33%	7440
February	1st to 10th	Night	6% 12% 4 13% 7% 6% 8% 5% 7% 7% 25%	2735
	11th to 20th	Night	5% 11% 3 11% 8% 7% 6% 6% 7% 7% 28%	2532
	21st to end	Night	4 9% 4 10% 9% 7% 6% 5% 7% 10% 30%	2145
March	1st to 10th	Night	5% 10% 5% 11% 7% 5% 6% 5% 7% 10% 28%	5302
	11th to 20th	Night	4 10% 5% 12% 8% 7% 6% 5% 7% 8% 29%	5000
	21st to end	Night	11% 13% 5% 14% 6% 5% 4 4 5% 7% 26%	5489
April	1st to 10th	Night	6% 11% 3 7% 6% 5% 4 5% 7% 7% 38%	1905
	11th to 20th	Night	9% 11% 3 10% 6% 6% 6% 4 7% 7% 30%	1781
	21st to end	Night	13% 10% 3 9% 4 4 4 3 7% 8% 35%	1750
May	1st to 10th	Night	15% 9% 3 8% 4 4 4 4 5% 6% 38%	3561
	11th to 20th	Night	14% 10% 2 8% 5% 5% 6% 5% 7% 9% 29%	3159
	21st to end	Night	13% 7% 3 7% 5% 5% 6% 5% 7% 7% 35%	3470
June	1st to 10th	Night	12% 8% 3 9% 5% 6% 6% 5% 7% 7% 32%	1400
	11th to 20th	Night	18% 11% 3 8% 5% 5% 4 4 7% 8% 27%	1400
	21st to end	Night	9% 5% 3 8% 6% 5% 7% 5% 8% 7% 39%	1400
July	1st to 10th	Night	8% 5% 2 6% 3 4 5% 4 8% 8% 47%	2290
	11th to 20th	Night	7% 4 2 4 4 4 4 5% 8% 9% 51%	2290
	21st to end	Night	8% 3 2 5% 4 3 4 4 6% 9% 54%	2414
August	1st to 10th	Night	14% 5% 2 5% 3 4 5% 4 6% 9% 45%	2293
	11th to 20th	Night	8% 5% 2 6% 4 4 4 4 8% 9% 46%	2811
	21st to end	Night	9% 5% 2 7% 4 5% 4 4 6% 8% 47%	3146
September	1st to 10th	Night	10% 6% 2 7% 4 4 4 4 5% 8% 47%	1810
	11th to 20th	Night	12% 6% 2 6% 3 4 4 3 5% 7% 47%	2019
	21st to end	Night	7% 6% 2 5% 4 4 4 4 6% 8% 49%	2095
October	1st to 10th	Night	8% 8% 2 6% 4 5% 5% 4 6% 9% 42%	3800
	11th to 20th	Night	7% 7% 3 7% 4 4 4 4 6% 9% 46%	3853
	21st to end	Night	7% 10% 4 8% 5% 4 4 4 6% 9% 38%	4610
November	1st to 10th	Night	12% 15% 4 9% 6% 5% 5% 4 5% 6% 29%	2730
	11th to 20th	Night	8% 10% 5% 14% 8% 7% 5% 4 6% 6% 25%	2820
	21st to end	Night	5% 11% 6% 13% 8% 5% 5% 4 6% 8% 29%	3000
December	1st to 10th	Night	9% 16% 5% 13% 7% 7% 6% 5% 5% 6% 19%	4890
	11th to 20th	Night	7% 15% 6% 14% 9% 7% 6% 5% 6% 7% 18%	5550
	21st to end	Night	3 7% 3 11% 8% 6% 5% 4 5% 7% 41%	7458

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	57% 6% 10% 20% 6%	3179
	11th to 20th	Day	49% 9% 14% 13% 14%	3180
	21st to end	Day	52% 8% 18% 17% 5%	3562
February	1st to 10th	Day	60% 5% 11% 17% 7%	1665
	11th to 20th	Day	55% 8% 12% 15% 9% 1	1764
	21st to end	Day	52% 9% 13% 18% 7%	1485
March	1st to 10th	Day	49% 6% 21% 18% 6%	4586
	11th to 20th	Day	52% 7% 16% 17% 7%	5000
	21st to end	Day	56% 9% 10% 19% 6%	5486
April	1st to 10th	Day	49% 7% 14% 20% 9% 1	2495
	11th to 20th	Day	50% 7% 14% 20% 8% 1	2570
	21st to end	Day	47% 8% 16% 19% 9% 1	2649
May	1st to 10th	Day	46% 5% 9% 23% 13% 3	6401
	11th to 20th	Day	52% 9% 11% 19% 8%	6738
	21st to end	Day	37% 12% 16% 22% 11% 2	7406
June	1st to 10th	Day	46% 9% 14% 21% 9% 1	3000
	11th to 20th	Day	56% 10% 15% 15% 4 1	3000
	21st to end	Day	40% 11% 22% 19% 7% 1	3000
July	1st to 10th	Day	33% 8% 21% 26% 11% 1	4816
	11th to 20th	Day	36% 8% 17% 28% 11%	4809
	21st to end	Day	30% 8% 21% 31% 9%	4977
August	1st to 10th	Day	38% 9% 17% 33% 3	4618
	11th to 20th	Day	31% 8% 24% 29% 8%	4067
	21st to end	Day	33% 6% 25% 30% 5%	4520
September	1st to 10th	Day	37% 9% 18% 24% 9% 3	2370
	11th to 20th	Day	43% 6% 17% 26% 7%	2160
	21st to end	Day	34% 9% 17% 29% 9% 3	2085
October	1st to 10th	Day	41% 6% 23% 24% 6%	3170
	11th to 20th	Day	40% 5% 16% 31% 8%	3073
	21st to end	Day	40% 7% 21% 28% 4	2916
November	1st to 10th	Day	58% 5% 14% 18% 5% 1	1568
	11th to 20th	Day	56% 9% 17% 15% 3	1575
	21st to end	Day	53% 8% 18% 17% 4	1400
December	1st to 10th	Day	57% 9% 18% 12% 4	2290
	11th to 20th	Day	60% 6% 15% 14% 3	2644
	21st to end	Day	46% 4 10% 27% 12% 1	3498
January	1st to 10th	Night	56% 8% 14% 13% 8%	6766
	11th to 20th	Night	49% 6% 14% 15% 14% 1	6780
	21st to end	Night	50% 6% 18% 22% 4	7440
February	1st to 10th	Night	54% 6% 14% 16% 9% 1	2735
	11th to 20th	Night	50% 8% 14% 17% 11%	2533
	21st to end	Night	46% 9% 14% 21% 9% 1	2145
March	1st to 10th	Night	48% 7% 20% 18% 7%	5302
	11th to 20th	Night	49% 8% 17% 20% 6%	5000
	21st to end	Night	53% 10% 11% 17% 9%	5489
April	1st to 10th	Night	41% 8% 15% 20% 14% 1	1905
	11th to 20th	Night	49% 8% 13% 17% 11% 2	1781
	21st to end	Night	44% 7% 14% 21% 12% 2	1750
May	1st to 10th	Night	45% 6% 7% 24% 16% 2	3561
	11th to 20th	Night	46% 9% 15% 21% 9% 1	3159
	21st to end	Night	41% 12% 17% 20% 9% 1	3470
June	1st to 10th	Night	45% 9% 15% 21% 10% 1	1400
	11th to 20th	Night	52% 9% 16% 16% 7%	1400
	21st to end	Night	39% 11% 21% 22% 7% 1	1400
July	1st to 10th	Night	33% 8% 22% 20% 16% 1	2255
	11th to 20th	Night	27% 8% 18% 31% 16%	2248
	21st to end	Night	27% 6% 23% 32% 11% 1	2337
August	1st to 10th	Night	36% 8% 18% 34% 3	2286
	11th to 20th	Night	33% 7% 21% 31% 8%	2838
	21st to end	Night	34% 5% 20% 31% 8%	3146
September	1st to 10th	Night	34% 9% 19% 23% 11% 4	1810
	11th to 20th	Night	36% 7% 17% 29% 9% 2	2019
	21st to end	Night	32% 8% 15% 30% 13% 2	2095
October	1st to 10th	Night	37% 7% 20% 29% 7% 1	3800
	11th to 20th	Night	35% 5% 16% 35% 9%	3853
	21st to end	Night	42% 6% 22% 26% 5%	4610
November	1st to 10th	Night	55% 7% 14% 17% 7% 1	2730
	11th to 20th	Night	57% 7% 15% 15% 5% 1	2820
	21st to end	Night	52% 8% 18% 17% 5%	3000
December	1st to 10th	Night	64% 6% 13% 11% 4 1	4890
	11th to 20th	Night	63% 7% 15% 10% 4	5547
	21st to end	Night	42% 5% 14% 22% 15% 2	7458

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	11% 5% 32% 34% 16% 3	200
	11th to 20th	Day	10% 12% 28% 29% 20% 2	200
	21st to end	Day	12% 12% 37% 28% 7% 3	220
February	1st to 10th	Day	11% 10% 34% 29% 12% 5%	233
	11th to 20th	Day	10% 7% 32% 31% 16% 4	300
	21st to end	Day	9% 6% 32% 33% 16% 5%	249
March	1st to 10th	Day	11% 9% 30% 35% 14% 1	450
	11th to 20th	Day	10% 8% 36% 29% 11% 5%	500
	21st to end	Day	15% 9% 30% 29% 15% 2	550
April	1st to 10th	Day	11% 11% 36% 29% 10% 3	500
	11th to 20th	Day	15% 11% 29% 31% 11% 3	492
	21st to end	Day	16% 12% 28% 29% 12% 3	549
May	1st to 10th	Day	13% 12% 26% 29% 16% 4	703
	11th to 20th	Day	12% 8% 27% 30% 17% 6%	725
	21st to end	Day	16% 9% 23% 28% 18% 7%	789
June	1st to 10th	Day	16% 10% 25% 34% 12% 3	730
	11th to 20th	Day	19% 10% 26% 26% 14% 5%	730
	21st to end	Day	12% 8% 22% 29% 20% 8%	730
July	1st to 10th	Day	10% 6% 19% 32% 25% 7%	721
	11th to 20th	Day	12% 7% 23% 32% 17% 9%	718
	21st to end	Day	10% 3 22% 31% 26% 9%	740
August	1st to 10th	Day	11% 6% 19% 32% 24% 8%	661
	11th to 20th	Day	9% 6% 24% 34% 21% 6%	477
	21st to end	Day	13% 8% 21% 29% 21% 8%	539
September	1st to 10th	Day	14% 7% 33% 27% 16% 3	490
	11th to 20th	Day	21% 8% 26% 29% 13% 2	490
	21st to end	Day	14% 14% 27% 31% 12% 3	485
October	1st to 10th	Day	13% 9% 27% 33% 14% 3	300
	11th to 20th	Day	16% 9% 31% 31% 11% 2	300
	21st to end	Day	10% 11% 41% 25% 10% 3	330
November	1st to 10th	Day	18% 8% 31% 33% 9% 1	300
	11th to 20th	Day	13% 9% 41% 28% 7% 1	287
	21st to end	Day	5% 10% 39% 32% 10% 5%	200
December	1st to 10th	Day	11% 8% 32% 32% 14% 5%	200
	11th to 20th	Day	11% 11% 36% 28% 15%	200
	21st to end	Day	7% 5% 31% 33% 17% 5%	220
January	1st to 10th	Night	11% 7% 32% 36% 12% 2	1000
	11th to 20th	Night	10% 8% 36% 32% 13% 1	1000
	21st to end	Night	13% 10% 37% 30% 8% 1	1095
February	1st to 10th	Night	10% 8% 26% 39% 15% 3	800
	11th to 20th	Night	9% 6% 32% 36% 15% 2	784
	21st to end	Night	7% 5% 27% 38% 20% 4	660
March	1st to 10th	Night	11% 5% 30% 39% 14% 2	800
	11th to 20th	Night	10% 5% 33% 35% 16% 2	800
	21st to end	Night	13% 6% 31% 34% 14% 2	880
April	1st to 10th	Night	9% 9% 28% 37% 14% 3	615
	11th to 20th	Night	13% 7% 34% 34% 11% 1	593
	21st to end	Night	15% 8% 26% 36% 15%	600
May	1st to 10th	Night	14% 8% 26% 36% 14% 2	573
	11th to 20th	Night	13% 6% 25% 37% 18% 2	394
	21st to end	Night	18% 6% 21% 33% 20% 2	433
June	1st to 10th	Night	17% 7% 26% 35% 14% 2	400
	11th to 20th	Night	23% 5% 24% 29% 18% 2	400
	21st to end	Night	12% 4 21% 39% 24% 2	400
July	1st to 10th	Night	10% 5% 20% 38% 26%	390
	11th to 20th	Night	11% 3 21% 44% 18% 3	388
	21st to end	Night	7% 5% 20% 40% 23% 5%	416
August	1st to 10th	Night	10% 3 19% 36% 25% 7%	410
	11th to 20th	Night	11% 4 18% 41% 23% 2	564
	21st to end	Night	10% 3 23% 40% 23% 1	627
September	1st to 10th	Night	14% 3 25% 37% 19% 2	570
	11th to 20th	Night	14% 5% 21% 43% 16% 1	689
	21st to end	Night	10% 5% 33% 34% 17% 1	760
October	1st to 10th	Night	14% 5% 30% 36% 15% 1	760
	11th to 20th	Night	13% 5% 33% 36% 13% 1	760
	21st to end	Night	15% 7% 34% 35% 9% 1	927
November	1st to 10th	Night	18% 7% 32% 32% 9% 2	975
	11th to 20th	Night	14% 7% 35% 31% 10% 3	1000
	21st to end	Night	9% 7% 38% 34% 11% 1	1000
December	1st to 10th	Night	12% 9% 33% 28% 15% 3	1000
	11th to 20th	Night	13% 9% 36% 31% 11% 1	1000
	21st to end	Night	10% 4 33% 35% 16% 3	1100

Page generated at 2025-07-17 23:10:03. Version ac07

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