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 2024-11-04.

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%	105630
	Night	8% 9% 4 9% 6% 5% 5% 5% 6% 8% 35%	101972
Transparency	Day	44% 9% 17% 22% 7%	105371
	Night	44% 8% 17% 22% 8% 1	101877
Seeing	Day	13% 8% 27% 30% 16% 5%	15586
	Night	12% 6% 30% 35% 15% 2	24625

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% 17% 11% 8% 5% 3 6% 5% 25%	2219
	11th to 20th	Day	6% 8% 4 9% 8% 9% 9% 11% 9% 6% 23%	2199
	21st to end	Day	7% 14% 5% 12% 7% 5% 5% 4 6% 6% 29%	2478
February	1st to 10th	Day	8% 14% 6% 14% 9% 7% 5% 4 5% 7% 23%	1581
	11th to 20th	Day	7% 13% 5% 13% 8% 6% 5% 4 5% 8% 25%	1665
	21st to end	Day	4 14% 5% 12% 8% 6% 7% 6% 9% 8% 21%	1413
March	1st to 10th	Day	5% 13% 5% 10% 7% 7% 7% 6% 8% 7% 25%	3182
	11th to 20th	Day	5% 9% 6% 13% 5% 3 3 4 6% 11% 35%	3489
	21st to end	Day	7% 12% 5% 16% 9% 5% 5% 4 4 6% 27%	3825
April	1st to 10th	Day	8% 14% 4 9% 7% 5% 5% 4 5% 7% 32%	2370
	11th to 20th	Day	12% 12% 5% 10% 5% 4 5% 4 5% 7% 31%	2440
	21st to end	Day	13% 12% 4 7% 4 5% 5% 4 7% 8% 31%	2516
May	1st to 10th	Day	16% 12% 5% 9% 6% 6% 5% 4 5% 5% 28%	4478
	11th to 20th	Day	12% 13% 3 9% 6% 5% 6% 4 7% 7% 28%	4694
	21st to end	Day	12% 7% 3 9% 7% 6% 6% 5% 8% 9% 28%	5161
June	1st to 10th	Day	15% 6% 3 7% 6% 6% 6% 4 7% 8% 31%	2850
	11th to 20th	Day	19% 9% 3 10% 6% 6% 6% 5% 8% 7% 22%	2850
	21st to end	Day	12% 6% 2 5% 6% 5% 6% 6% 8% 9% 35%	2850
July	1st to 10th	Day	8% 5% 2 5% 4 5% 4 5% 7% 8% 47%	4740
	11th to 20th	Day	10% 5% 2 6% 4 5% 4 4 6% 8% 44%	4740
	21st to end	Day	7% 5% 2 5% 4 4 5% 4 7% 9% 49%	5138
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% 13% 5% 11% 7% 5% 5% 4 4 7% 26%	1512
	11th to 20th	Day	7% 13% 6% 14% 8% 5% 4 4 7% 7% 24%	1497
	21st to end	Day	6% 13% 6% 12% 6% 6% 5% 4 6% 9% 27%	1330
December	1st to 10th	Day	8% 13% 5% 11% 7% 8% 8% 5% 7% 6% 22%	1330
	11th to 20th	Day	7% 11% 4 12% 8% 9% 6% 4 7% 7% 24%	1682
	21st to end	Day	4 9% 4 9% 6% 5% 5% 3 5% 9% 42%	2442
January	1st to 10th	Night	5% 10% 5% 15% 8% 8% 7% 6% 7% 7% 21%	4726
	11th to 20th	Night	3 8% 3 9% 9% 8% 9% 8% 8% 9% 26%	4699
	21st to end	Night	6% 13% 6% 10% 6% 5% 5% 4 6% 7% 31%	5210
February	1st to 10th	Night	6% 12% 4 13% 7% 6% 8% 5% 7% 7% 26%	2599
	11th to 20th	Night	6% 11% 3 11% 8% 7% 6% 6% 7% 7% 28%	2402
	21st to end	Night	4 10% 4 11% 9% 7% 6% 5% 7% 9% 30%	2041
March	1st to 10th	Night	6% 12% 5% 13% 7% 5% 5% 5% 6% 10% 26%	3688
	11th to 20th	Night	4 8% 4 11% 6% 5% 5% 5% 7% 9% 36%	3490
	21st to end	Night	7% 10% 4 14% 7% 6% 5% 5% 7% 9% 26%	3828
April	1st to 10th	Night	6% 11% 3 7% 6% 5% 4 5% 7% 7% 38%	1810
	11th to 20th	Night	9% 11% 3 11% 6% 6% 6% 4 7% 7% 29%	1691
	21st to end	Night	13% 10% 3 9% 4 4 4 3 7% 8% 34%	1663
May	1st to 10th	Night	21% 12% 4 8% 5% 4 4 4 4 6% 27%	2489
	11th to 20th	Night	12% 9% 2 7% 5% 5% 6% 5% 7% 9% 33%	2199
	21st to end	Night	14% 7% 4 9% 6% 5% 7% 5% 7% 7% 28%	2414
June	1st to 10th	Night	12% 8% 3 9% 5% 6% 6% 5% 7% 7% 31%	1330
	11th to 20th	Night	18% 11% 3 8% 5% 5% 4 4 6% 8% 27%	1330
	21st to end	Night	9% 4 3 8% 6% 5% 7% 5% 8% 7% 39%	1330
July	1st to 10th	Night	8% 5% 2 6% 3 4 6% 4 7% 8% 47%	2220
	11th to 20th	Night	6% 4 2 4 4 4 4 5% 8% 9% 51%	2220
	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% 28%	2639
	11th to 20th	Night	9% 10% 5% 14% 8% 7% 5% 4 6% 6% 25%	2679
	21st to end	Night	5% 11% 5% 13% 8% 5% 5% 4 6% 8% 29%	2850
December	1st to 10th	Night	6% 14% 5% 12% 8% 7% 7% 4 6% 7% 26%	2850
	11th to 20th	Night	7% 13% 6% 14% 10% 7% 6% 5% 6% 7% 21%	3510
	21st to end	Night	3 8% 3 8% 6% 6% 5% 4 5% 7% 45%	5214

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	58% 8% 12% 17% 5%	2219
	11th to 20th	Day	50% 11% 13% 15% 9% 1	2220
	21st to end	Day	52% 9% 14% 19% 6%	2478
February	1st to 10th	Day	60% 6% 11% 17% 5%	1581
	11th to 20th	Day	55% 8% 13% 15% 8% 1	1674
	21st to end	Day	53% 9% 13% 18% 7%	1413
March	1st to 10th	Day	52% 8% 18% 15% 7%	3182
	11th to 20th	Day	43% 9% 22% 17% 9%	3490
	21st to end	Day	52% 11% 12% 18% 6%	3825
April	1st to 10th	Day	50% 7% 15% 19% 9% 1	2370
	11th to 20th	Day	50% 7% 14% 20% 8% 1	2440
	21st to end	Day	47% 9% 16% 19% 8% 1	2516
May	1st to 10th	Day	56% 7% 11% 20% 6%	4478
	11th to 20th	Day	48% 11% 12% 20% 9% 1	4698
	21st to end	Day	43% 16% 17% 16% 8%	5162
June	1st to 10th	Day	47% 9% 15% 20% 8% 1	2850
	11th to 20th	Day	56% 10% 15% 15% 4 1	2850
	21st to end	Day	40% 11% 22% 19% 7% 1	2850
July	1st to 10th	Day	33% 9% 21% 26% 11% 1	4666
	11th to 20th	Day	35% 8% 17% 28% 11%	4659
	21st to end	Day	30% 8% 21% 31% 9%	4976
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% 17% 5% 1	1512
	11th to 20th	Day	56% 9% 17% 15% 3	1497
	21st to end	Day	52% 9% 18% 17% 4	1330
December	1st to 10th	Day	56% 9% 14% 15% 6% 1	1330
	11th to 20th	Day	54% 9% 17% 16% 5%	1684
	21st to end	Day	40% 5% 12% 27% 15% 2	2442
January	1st to 10th	Night	55% 11% 15% 14% 5% 1	4726
	11th to 20th	Night	49% 7% 16% 17% 10% 1	4740
	21st to end	Night	50% 8% 15% 21% 6%	5210
February	1st to 10th	Night	54% 7% 15% 17% 8% 1	2599
	11th to 20th	Night	50% 8% 15% 16% 11%	2403
	21st to end	Night	47% 9% 13% 21% 8% 1	2041
March	1st to 10th	Night	51% 9% 16% 18% 6%	3688
	11th to 20th	Night	40% 10% 22% 21% 7% 1	3490
	21st to end	Night	47% 13% 15% 18% 6%	3828
April	1st to 10th	Night	41% 8% 16% 20% 14% 1	1810
	11th to 20th	Night	50% 9% 13% 17% 10% 2	1691
	21st to end	Night	45% 7% 15% 20% 11% 2	1663
May	1st to 10th	Night	56% 8% 8% 21% 7% 1	2489
	11th to 20th	Night	40% 12% 14% 21% 12% 1	2199
	21st to end	Night	44% 15% 17% 17% 5% 1	2414
June	1st to 10th	Night	46% 9% 15% 21% 9% 1	1330
	11th to 20th	Night	52% 9% 15% 16% 7%	1330
	21st to end	Night	38% 11% 21% 22% 7% 1	1330
July	1st to 10th	Night	33% 8% 21% 19% 17% 1	2185
	11th to 20th	Night	26% 8% 19% 31% 16% 1	2178
	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% 16% 7% 1	2639
	11th to 20th	Night	57% 7% 15% 15% 5% 1	2679
	21st to end	Night	51% 8% 19% 17% 5%	2850
December	1st to 10th	Night	56% 7% 13% 16% 7% 2	2850
	11th to 20th	Night	59% 9% 15% 11% 6%	3507
	21st to end	Night	37% 6% 16% 21% 17% 3	5214

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	10% 5% 31% 33% 17% 3	180
	11th to 20th	Day	10% 12% 25% 29% 22% 2	180
	21st to end	Day	12% 11% 34% 31% 8% 4	198
February	1st to 10th	Day	12% 11% 33% 29% 11% 4	209
	11th to 20th	Day	11% 8% 31% 28% 17% 4	270
	21st to end	Day	10% 5% 30% 32% 17% 5%	225
March	1st to 10th	Day	12% 9% 30% 34% 13% 1	412
	11th to 20th	Day	10% 8% 37% 29% 12% 5%	460
	21st to end	Day	14% 8% 31% 30% 15% 3	506
April	1st to 10th	Day	12% 12% 37% 27% 9% 3	460
	11th to 20th	Day	15% 10% 27% 33% 12% 3	452
	21st to end	Day	17% 12% 28% 29% 11% 2	506
May	1st to 10th	Day	14% 11% 25% 29% 16% 4	653
	11th to 20th	Day	10% 8% 27% 31% 17% 6%	675
	21st to end	Day	16% 8% 23% 28% 19% 7%	734
June	1st to 10th	Day	16% 9% 25% 34% 12% 3	680
	11th to 20th	Day	19% 10% 26% 26% 14% 5%	680
	21st to end	Day	12% 8% 21% 30% 21% 9%	680
July	1st to 10th	Day	10% 5% 18% 33% 26% 7%	671
	11th to 20th	Day	12% 7% 24% 33% 16% 9%	668
	21st to end	Day	10% 3 22% 31% 26% 9%	739
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% 29% 33% 10% 1	279
	11th to 20th	Day	14% 10% 40% 28% 7% 1	259
	21st to end	Day	5% 11% 40% 31% 9% 4	180
December	1st to 10th	Day	11% 7% 33% 29% 15% 5%	180
	11th to 20th	Day	10% 11% 36% 28% 15%	180
	21st to end	Day	8% 5% 33% 32% 17% 5%	198
January	1st to 10th	Night	11% 7% 32% 36% 12% 2	950
	11th to 20th	Night	10% 8% 35% 32% 13% 1	950
	21st to end	Night	13% 10% 36% 32% 8% 1	1041
February	1st to 10th	Night	10% 8% 25% 39% 15% 3	760
	11th to 20th	Night	10% 7% 33% 34% 14% 2	744
	21st to end	Night	7% 4 25% 38% 21% 4	628
March	1st to 10th	Night	11% 5% 31% 38% 14% 2	760
	11th to 20th	Night	10% 5% 33% 34% 16% 2	760
	21st to end	Night	12% 6% 31% 34% 14% 3	836
April	1st to 10th	Night	10% 9% 28% 36% 15% 3	584
	11th to 20th	Night	14% 7% 32% 35% 11% 1	563
	21st to end	Night	16% 8% 27% 36% 14%	570
May	1st to 10th	Night	14% 8% 26% 35% 14% 2	545
	11th to 20th	Night	11% 5% 25% 38% 18% 2	374
	21st to end	Night	18% 6% 21% 32% 20% 2	411
June	1st to 10th	Night	17% 6% 27% 34% 14% 2	380
	11th to 20th	Night	24% 5% 24% 28% 17% 2	380
	21st to end	Night	11% 4 22% 38% 24% 2	380
July	1st to 10th	Night	11% 5% 20% 38% 27%	370
	11th to 20th	Night	10% 3 21% 44% 18% 3	368
	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% 31% 32% 9% 2	943
	11th to 20th	Night	14% 7% 33% 32% 11% 3	950
	21st to end	Night	9% 7% 38% 34% 11% 1	950
December	1st to 10th	Night	12% 8% 33% 29% 15% 4	950
	11th to 20th	Night	12% 9% 36% 30% 11% 1	950
	21st to end	Night	10% 4 33% 35% 16% 3	1045

Page generated at 2024-11-01 20:47:40. Version ac07

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