Fort Chipewyan
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Fort Chipewyan clear sky chart from 2005-11-06 to 2025-02-25.

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	9% 9% 4 9% 6% 5% 6% 5% 7% 8% 34%	111034
	Night	8% 12% 5% 11% 7% 6% 6% 5% 6% 7% 28%	116198
Transparency	Day	27% 45% 8% 15% 4	110747
	Night	33% 42% 8% 14% 4	116132
Seeing	Day	13% 8% 28% 31% 16% 4	16995
	Night	13% 7% 27% 33% 17% 3	25482

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	5% 11% 6% 20% 12% 9% 9% 5% 4 4 16%	2259
	11th to 20th	Day	5% 9% 4 13% 8% 7% 10% 7% 8% 6% 22%	2491
	21st to end	Day	7% 18% 6% 11% 8% 7% 6% 5% 7% 7% 18%	3498
February	1st to 10th	Day	4 10% 5% 13% 10% 8% 8% 6% 7% 7% 21%	1430
	11th to 20th	Day	6% 11% 5% 11% 8% 5% 6% 6% 7% 8% 27%	1647
	21st to end	Day	3 11% 6% 13% 9% 6% 7% 7% 9% 6% 21%	1449
March	1st to 10th	Day	4 12% 6% 11% 7% 6% 8% 5% 9% 7% 26%	3000
	11th to 20th	Day	5% 10% 4 12% 7% 6% 6% 5% 7% 7% 31%	3489
	21st to end	Day	3 7% 5% 10% 6% 4 4 4 6% 7% 44%	3855
April	1st to 10th	Day	7% 14% 4 9% 5% 4 4 4 5% 6% 37%	2460
	11th to 20th	Day	7% 10% 3 8% 6% 6% 5% 4 6% 6% 39%	2440
	21st to end	Day	7% 10% 3 9% 7% 6% 5% 5% 7% 8% 33%	2717
May	1st to 10th	Day	8% 9% 3 8% 6% 6% 6% 4 7% 8% 36%	4740
	11th to 20th	Day	12% 10% 3 8% 5% 5% 5% 4 7% 8% 33%	4851
	21st to end	Day	12% 6% 2 5% 4 4 5% 5% 8% 9% 40%	5722
June	1st to 10th	Day	12% 8% 2 8% 5% 6% 6% 5% 7% 7% 35%	3230
	11th to 20th	Day	12% 8% 3 8% 5% 5% 6% 4 7% 8% 34%	3230
	21st to end	Day	8% 5% 3 6% 6% 5% 6% 6% 7% 8% 41%	3230
July	1st to 10th	Day	6% 4 2 6% 6% 6% 7% 5% 9% 12% 38%	5380
	11th to 20th	Day	8% 5% 2 5% 4 4 5% 4 7% 8% 49%	5380
	21st to end	Day	12% 5% 2 6% 4 4 5% 4 7% 9% 40%	5287
August	1st to 10th	Day	5% 4 2 6% 4 5% 5% 5% 7% 7% 50%	4720
	11th to 20th	Day	11% 6% 3 8% 5% 4 5% 4 6% 8% 43%	4518
	21st to end	Day	13% 7% 3 8% 5% 5% 6% 4 6% 9% 33%	4521
September	1st to 10th	Day	13% 8% 3 8% 5% 4 4 4 6% 8% 37%	2438
	11th to 20th	Day	15% 9% 3 8% 5% 5% 6% 4 7% 7% 32%	2187
	21st to end	Day	14% 8% 4 8% 6% 5% 5% 4 7% 7% 32%	2071
October	1st to 10th	Day	9% 11% 4 9% 6% 7% 6% 4 5% 5% 33%	3170
	11th to 20th	Day	11% 14% 4 9% 5% 4 4 3 5% 7% 33%	2861
	21st to end	Day	9% 12% 5% 12% 6% 6% 6% 5% 5% 8% 25%	2754
November	1st to 10th	Day	13% 17% 6% 13% 6% 4 5% 4 5% 7% 21%	1483
	11th to 20th	Day	10% 17% 5% 15% 9% 7% 5% 4 6% 5% 17%	1255
	21st to end	Day	9% 16% 7% 15% 8% 7% 6% 3 5% 5% 20%	1200
December	1st to 10th	Day	5% 19% 7% 19% 11% 10% 7% 4 4 8% 8%	1706
	11th to 20th	Day	6% 16% 8% 15% 7% 6% 5% 6% 4 8% 19%	1879
	21st to end	Day	5% 14% 5% 13% 6% 7% 6% 4 5% 6% 28%	2486
January	1st to 10th	Night	5% 14% 7% 16% 10% 9% 8% 5% 6% 5% 15%	7686
	11th to 20th	Night	4 9% 4 12% 9% 7% 10% 7% 7% 6% 24%	7390
	21st to end	Night	6% 18% 7% 13% 7% 6% 6% 5% 5% 7% 21%	7458
February	1st to 10th	Night	3 8% 6% 12% 9% 9% 10% 6% 6% 7% 24%	2987
	11th to 20th	Night	4 11% 4 12% 8% 7% 7% 6% 6% 7% 28%	2638
	21st to end	Night	3 11% 4 12% 10% 7% 8% 6% 6% 7% 26%	2099
March	1st to 10th	Night	3 10% 6% 11% 8% 7% 6% 6% 6% 7% 30%	3867
	11th to 20th	Night	4 9% 4 12% 7% 5% 6% 5% 7% 8% 33%	3490
	21st to end	Night	3 8% 5% 12% 6% 5% 5% 5% 6% 6% 40%	3797
April	1st to 10th	Night	9% 11% 5% 10% 6% 6% 6% 5% 6% 7% 30%	1718
	11th to 20th	Night	7% 9% 3 8% 5% 5% 6% 4 7% 8% 39%	1691
	21st to end	Night	7% 10% 4 10% 6% 5% 5% 5% 5% 8% 35%	1460
May	1st to 10th	Night	9% 10% 4 8% 6% 4 5% 5% 6% 8% 36%	2220
	11th to 20th	Night	11% 9% 3 8% 5% 5% 5% 4 8% 9% 33%	2042
	21st to end	Night	11% 7% 3 6% 5% 5% 5% 4 7% 9% 38%	1851
June	1st to 10th	Night	12% 8% 3 8% 6% 5% 4 5% 8% 7% 34%	950
	11th to 20th	Night	15% 8% 2 7% 6% 5% 5% 6% 6% 8% 33%	950
	21st to end	Night	7% 5% 3 6% 6% 5% 4 5% 8% 8% 41%	950
July	1st to 10th	Night	6% 4 2 6% 5% 7% 7% 6% 9% 12% 37%	1580
	11th to 20th	Night	7% 5% 2 6% 4 4 4 4 8% 10% 45%	1580
	21st to end	Night	15% 4 2 6% 4 5% 5% 5% 8% 10% 37%	2249
August	1st to 10th	Night	9% 5% 2 5% 4 4 4 3 6% 7% 52%	2210
	11th to 20th	Night	10% 4 2 5% 4 6% 6% 4 7% 8% 45%	2295
	21st to end	Night	15% 5% 3 8% 6% 5% 6% 5% 7% 8% 31%	3146
September	1st to 10th	Night	12% 7% 3 8% 6% 4 5% 4 6% 7% 39%	1742
	11th to 20th	Night	15% 7% 3 5% 4 4 4 4 6% 8% 39%	1990
	21st to end	Night	11% 8% 4 9% 6% 6% 5% 3 6% 7% 35%	2109
October	1st to 10th	Night	9% 12% 3 8% 5% 5% 5% 4 5% 8% 36%	3800
	11th to 20th	Night	13% 13% 4 8% 5% 4 5% 4 5% 7% 32%	4038
	21st to end	Night	13% 17% 5% 13% 7% 6% 6% 4 5% 5% 18%	4799
November	1st to 10th	Night	11% 17% 6% 12% 7% 6% 5% 4 5% 5% 22%	2815
	11th to 20th	Night	9% 17% 6% 16% 9% 6% 5% 4 6% 5% 18%	3145
	21st to end	Night	9% 17% 7% 14% 9% 6% 5% 4 5% 6% 17%	3200
December	1st to 10th	Night	7% 18% 7% 15% 9% 8% 8% 4 5% 7% 11%	5473
	11th to 20th	Night	6% 16% 6% 12% 9% 8% 7% 5% 6% 7% 19%	6313
	21st to end	Night	4 15% 5% 11% 6% 5% 5% 4 6% 7% 32%	8470

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% 27% 5% 9% 2	2259
	11th to 20th	Day	43% 26% 8% 19% 4	2508
	21st to end	Day	48% 30% 10% 10% 2	3498
February	1st to 10th	Day	24% 63% 4 6% 3	1430
	11th to 20th	Day	22% 62% 5% 9% 2	1655
	21st to end	Day	22% 63% 4 7% 4	1449
March	1st to 10th	Day	35% 40% 7% 17% 1	3000
	11th to 20th	Day	30% 39% 8% 18% 4	3490
	21st to end	Day	23% 39% 3 21% 13%	3855
April	1st to 10th	Day	14% 65% 5% 10% 6%	2460
	11th to 20th	Day	15% 65% 3 10% 7%	2440
	21st to end	Day	15% 65% 4 12% 3	2717
May	1st to 10th	Day	30% 40% 8% 11% 11% 1	4740
	11th to 20th	Day	32% 38% 6% 16% 7%	4855
	21st to end	Day	26% 39% 8% 20% 6%	5723
June	1st to 10th	Day	20% 65% 5% 6% 3	3230
	11th to 20th	Day	16% 66% 4 9% 4	3230
	21st to end	Day	12% 66% 7% 9% 5%	3230
July	1st to 10th	Day	23% 41% 15% 18% 4	5296
	11th to 20th	Day	16% 38% 10% 31% 5% 1	5287
	21st to end	Day	25% 38% 12% 24% 1	5119
August	1st to 10th	Day	16% 39% 9% 31% 5%	4702
	11th to 20th	Day	23% 40% 9% 19% 9% 1	4563
	21st to end	Day	29% 41% 16% 13% 1	4520
September	1st to 10th	Day	20% 62% 9% 8% 2	2438
	11th to 20th	Day	18% 61% 7% 12% 2	2187
	21st to end	Day	19% 61% 8% 9% 3	2071
October	1st to 10th	Day	31% 38% 12% 16% 3	3170
	11th to 20th	Day	32% 38% 9% 17% 4	2861
	21st to end	Day	34% 42% 13% 11% 1	2754
November	1st to 10th	Day	27% 58% 7% 7%	1483
	11th to 20th	Day	29% 59% 5% 6%	1255
	21st to end	Day	30% 58% 4 6% 2	1200
December	1st to 10th	Day	52% 37% 3 6% 1	1706
	11th to 20th	Day	45% 32% 5% 12% 5%	1880
	21st to end	Day	41% 27% 12% 17% 3	2486
January	1st to 10th	Night	53% 27% 7% 11% 2	7686
	11th to 20th	Night	40% 27% 7% 21% 5%	7435
	21st to end	Night	47% 30% 10% 11% 2	7458
February	1st to 10th	Night	23% 64% 4 7% 2	2987
	11th to 20th	Night	21% 62% 7% 8% 2	2640
	21st to end	Night	20% 64% 4 6% 5%	2099
March	1st to 10th	Night	32% 40% 11% 15% 3	3867
	11th to 20th	Night	26% 40% 8% 21% 5%	3490
	21st to end	Night	27% 39% 2 17% 15%	3797
April	1st to 10th	Night	16% 66% 5% 8% 5%	1718
	11th to 20th	Night	13% 65% 2 10% 10%	1691
	21st to end	Night	14% 65% 2 13% 5%	1460
May	1st to 10th	Night	29% 39% 6% 16% 8%	2220
	11th to 20th	Night	32% 38% 6% 15% 8%	2042
	21st to end	Night	27% 39% 6% 19% 8%	1851
June	1st to 10th	Night	18% 67% 5% 9% 2	950
	11th to 20th	Night	14% 66% 3 10% 7%	950
	21st to end	Night	13% 65% 7% 10% 5%	950
July	1st to 10th	Night	22% 40% 14% 19% 4	1555
	11th to 20th	Night	18% 38% 8% 28% 7% 1	1550
	21st to end	Night	26% 39% 13% 20% 1	2179
August	1st to 10th	Night	18% 38% 6% 30% 8%	2203
	11th to 20th	Night	20% 40% 12% 17% 8% 2	2316
	21st to end	Night	29% 40% 18% 11% 1	3146
September	1st to 10th	Night	19% 61% 8% 9% 3	1742
	11th to 20th	Night	13% 61% 8% 15% 2	1990
	21st to end	Night	18% 60% 7% 10% 4	2109
October	1st to 10th	Night	28% 39% 9% 22% 2	3800
	11th to 20th	Night	34% 38% 11% 15% 2	4038
	21st to end	Night	44% 39% 6% 10% 1	4799
November	1st to 10th	Night	27% 58% 6% 8% 1	2815
	11th to 20th	Night	30% 59% 5% 6% 1	3145
	21st to end	Night	29% 58% 6% 5% 1	3200
December	1st to 10th	Night	50% 38% 6% 5% 2	5473
	11th to 20th	Night	45% 33% 8% 11% 3	6311
	21st to end	Night	36% 27% 15% 18% 5%	8470

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	12% 5% 30% 35% 17% 2	200
	11th to 20th	Day	15% 7% 33% 31% 13% 3	200
	21st to end	Day	13% 17% 30% 31% 7% 3	220
February	1st to 10th	Day	8% 7% 40% 28% 12% 7%	200
	11th to 20th	Day	8% 7% 34% 31% 14% 6%	245
	21st to end	Day	7% 9% 29% 34% 18% 4	237
March	1st to 10th	Day	7% 10% 35% 28% 17% 3	353
	11th to 20th	Day	9% 14% 37% 28% 11% 1	460
	21st to end	Day	9% 9% 34% 31% 13% 3	506
April	1st to 10th	Day	13% 13% 36% 24% 10% 4	460
	11th to 20th	Day	11% 12% 33% 28% 13% 2	452
	21st to end	Day	12% 10% 29% 34% 13% 2	644
May	1st to 10th	Day	14% 8% 27% 32% 16% 2	653
	11th to 20th	Day	12% 9% 24% 31% 20% 4	675
	21st to end	Day	13% 6% 25% 36% 16% 4	856
June	1st to 10th	Day	17% 10% 26% 29% 14% 4	870
	11th to 20th	Day	17% 9% 26% 30% 16% 3	870
	21st to end	Day	9% 6% 23% 36% 22% 5%	870
July	1st to 10th	Day	12% 6% 20% 38% 20% 5%	856
	11th to 20th	Day	11% 6% 19% 37% 21% 6%	852
	21st to end	Day	12% 5% 20% 30% 25% 9%	800
August	1st to 10th	Day	9% 5% 20% 31% 24% 11%	676
	11th to 20th	Day	15% 6% 27% 31% 16% 5%	643
	21st to end	Day	17% 6% 27% 29% 16% 5%	539
September	1st to 10th	Day	17% 9% 30% 27% 14% 3	490
	11th to 20th	Day	16% 8% 28% 28% 16% 4	490
	21st to end	Day	16% 13% 29% 26% 13% 3	471
October	1st to 10th	Day	19% 10% 32% 23% 10% 5%	300
	11th to 20th	Day	22% 8% 41% 21% 6% 2	300
	21st to end	Day	15% 12% 36% 22% 13% 1	330
November	1st to 10th	Day	15% 10% 34% 29% 11%	257
	11th to 20th	Day	18% 16% 34% 22% 9% 3	200
	21st to end	Day	17% 8% 36% 29% 10% 2	200
December	1st to 10th	Day	12% 8% 32% 32% 13% 4	200
	11th to 20th	Day	16% 6% 31% 28% 17% 3	200
	21st to end	Day	9% 5% 22% 40% 20% 5%	220
January	1st to 10th	Night	13% 8% 30% 31% 15% 3	1100
	11th to 20th	Night	14% 8% 33% 32% 12% 2	1099
	21st to end	Night	15% 8% 31% 32% 12% 2	1100
February	1st to 10th	Night	7% 7% 30% 33% 17% 5%	987
	11th to 20th	Night	9% 6% 30% 38% 16% 2	784
	21st to end	Night	7% 7% 30% 33% 21% 2	646
March	1st to 10th	Night	8% 8% 24% 33% 26% 3	760
	11th to 20th	Night	11% 7% 33% 35% 13% 1	760
	21st to end	Night	7% 6% 26% 38% 18% 4	817
April	1st to 10th	Night	12% 8% 29% 31% 17% 3	570
	11th to 20th	Night	10% 9% 23% 38% 18% 2	563
	21st to end	Night	12% 6% 27% 38% 16% 2	504
May	1st to 10th	Night	14% 8% 23% 36% 16% 3	380
	11th to 20th	Night	12% 7% 25% 33% 20% 3	374
	21st to end	Night	12% 4 24% 35% 22% 3	411
June	1st to 10th	Night	14% 5% 22% 36% 19% 5%	380
	11th to 20th	Night	18% 4 18% 36% 20% 3	380
	21st to end	Night	8% 3 19% 34% 33% 4	380
July	1st to 10th	Night	11% 4 18% 38% 24% 5%	370
	11th to 20th	Night	11% 4 15% 40% 26% 5%	368
	21st to end	Night	11% 3 14% 32% 33% 7%	416
August	1st to 10th	Night	11% 3 15% 33% 30% 8%	378
	11th to 20th	Night	11% 4 23% 39% 19% 3	418
	21st to end	Night	15% 4 22% 35% 21% 3	627
September	1st to 10th	Night	13% 6% 25% 33% 19% 3	570
	11th to 20th	Night	19% 5% 20% 36% 18% 3	660
	21st to end	Night	15% 8% 28% 33% 14% 1	760
October	1st to 10th	Night	18% 9% 31% 27% 13% 3	760
	11th to 20th	Night	18% 7% 31% 29% 13% 3	760
	21st to end	Night	19% 11% 28% 28% 11% 3	1040
November	1st to 10th	Night	19% 8% 28% 30% 13% 3	975
	11th to 20th	Night	18% 8% 31% 28% 13% 2	1000
	21st to end	Night	17% 10% 33% 28% 10% 3	1000
December	1st to 10th	Night	14% 7% 30% 32% 15% 2	1075
	11th to 20th	Night	13% 7% 30% 35% 12% 3	1100
	21st to end	Night	12% 5% 25% 35% 19% 4	1210

Page generated at 2025-02-22 04:51:40. Version ac07

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