Athabasca Falls
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Athabasca Falls clear sky chart from 2005-11-06 to 2024-12-02.

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	8% 14% 5% 12% 7% 6% 6% 4 6% 7% 24%	105909
	Night	5% 12% 6% 13% 8% 7% 6% 5% 7% 8% 24%	102288
Transparency	Day	59% 10% 12% 12% 6% 1	105652
	Night	58% 11% 13% 12% 6% 1	102191
Seeing	Day	19% 17% 31% 22% 9% 2	16125
	Night	11% 13% 39% 26% 10% 1	24458

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	1 10% 8% 20% 9% 11% 8% 5% 7% 7% 13%	1899
	11th to 20th	Day	2 9% 5% 17% 7% 7% 6% 6% 7% 7% 27%	2247
	21st to end	Day	2 19% 9% 14% 8% 7% 6% 5% 7% 9% 14%	2794
February	1st to 10th	Day	3 15% 6% 16% 8% 7% 7% 6% 6% 7% 19%	1520
	11th to 20th	Day	2 12% 6% 22% 8% 7% 7% 4 7% 7% 18%	1562
	21st to end	Day	1 11% 6% 18% 11% 9% 7% 4 8% 6% 19%	1565
March	1st to 10th	Day	8% 6% 17% 12% 10% 8% 6% 7% 7% 18%	3138
	11th to 20th	Day	2 14% 10% 14% 7% 6% 6% 4 5% 6% 27%	3251
	21st to end	Day	2 17% 8% 22% 9% 6% 5% 4 5% 6% 17%	4165
April	1st to 10th	Day	5% 20% 10% 19% 9% 6% 6% 4 6% 5% 10%	2280
	11th to 20th	Day	4 20% 8% 17% 9% 7% 5% 3 5% 6% 16%	2379
	21st to end	Day	7% 23% 6% 14% 6% 6% 4 3 6% 6% 18%	2603
May	1st to 10th	Day	10% 24% 5% 10% 6% 5% 5% 4 4 6% 22%	4420
	11th to 20th	Day	9% 21% 5% 10% 6% 5% 5% 4 7% 7% 20%	4582
	21st to end	Day	14% 28% 5% 11% 6% 5% 5% 4 4 5% 14%	5161
June	1st to 10th	Day	17% 14% 4 10% 7% 7% 6% 4 5% 6% 20%	3022
	11th to 20th	Day	22% 15% 5% 10% 7% 6% 6% 5% 5% 6% 14%	3040
	21st to end	Day	15% 11% 4 10% 7% 7% 7% 5% 5% 6% 23%	3040
July	1st to 10th	Day	14% 8% 3 8% 6% 5% 5% 4 5% 5% 38%	5060
	11th to 20th	Day	9% 6% 3 8% 6% 5% 5% 5% 6% 7% 41%	4999
	21st to end	Day	11% 9% 3 9% 7% 7% 7% 4 6% 7% 31%	4824
August	1st to 10th	Day	13% 8% 3 8% 5% 6% 6% 5% 6% 7% 34%	4401
	11th to 20th	Day	11% 9% 3 10% 7% 6% 8% 5% 7% 7% 28%	4330
	21st to end	Day	15% 10% 4 9% 5% 6% 6% 5% 6% 6% 29%	4448
September	1st to 10th	Day	14% 11% 5% 9% 5% 5% 5% 4 5% 5% 32%	2280
	11th to 20th	Day	12% 12% 4 8% 6% 5% 5% 4 6% 7% 32%	2214
	21st to end	Day	13% 16% 5% 11% 6% 5% 5% 4 5% 6% 26%	2090
October	1st to 10th	Day	5% 15% 6% 15% 7% 6% 6% 5% 6% 7% 22%	3247
	11th to 20th	Day	7% 15% 8% 15% 6% 5% 5% 4 5% 7% 22%	2891
	21st to end	Day	3 13% 7% 16% 8% 7% 5% 4 4 5% 27%	3101
November	1st to 10th	Day	4 19% 6% 13% 10% 7% 7% 5% 6% 6% 17%	1644
	11th to 20th	Day	2 11% 7% 13% 8% 7% 6% 7% 7% 8% 24%	1400
	21st to end	Day	2 14% 4 14% 9% 9% 7% 6% 7% 8% 22%	1400
December	1st to 10th	Day	4 12% 5% 15% 8% 9% 7% 6% 5% 7% 22%	1337
	11th to 20th	Day	1 11% 6% 14% 7% 8% 9% 7% 9% 10% 18%	1485
	21st to end	Day	12% 7% 12% 7% 7% 7% 6% 6% 9% 27%	2090
January	1st to 10th	Night	1 10% 7% 20% 12% 8% 8% 6% 7% 8% 12%	5046
	11th to 20th	Night	2 8% 5% 13% 8% 8% 7% 7% 9% 9% 24%	4668
	21st to end	Night	2 16% 9% 15% 9% 9% 8% 6% 6% 7% 14%	4862
February	1st to 10th	Night	4 13% 7% 16% 11% 9% 7% 6% 6% 7% 14%	2660
	11th to 20th	Night	3 11% 6% 15% 9% 9% 7% 6% 7% 8% 18%	2502
	21st to end	Night	1 13% 5% 14% 12% 8% 7% 6% 8% 8% 18%	1889
March	1st to 10th	Night	1 8% 6% 16% 12% 10% 7% 6% 8% 8% 18%	3736
	11th to 20th	Night	2 13% 8% 11% 7% 6% 6% 5% 7% 9% 25%	3728
	21st to end	Night	2 15% 8% 21% 9% 6% 5% 4 5% 6% 19%	3488
April	1st to 10th	Night	2 15% 10% 15% 9% 7% 7% 5% 7% 6% 16%	1900
	11th to 20th	Night	3 14% 6% 15% 9% 6% 6% 4 5% 8% 25%	1751
	21st to end	Night	5% 16% 5% 12% 7% 7% 6% 4 6% 6% 26%	1575
May	1st to 10th	Night	4 18% 6% 12% 6% 5% 5% 4 7% 8% 25%	2540
	11th to 20th	Night	8% 19% 4 8% 6% 4 5% 4 6% 8% 27%	2309
	21st to end	Night	10% 22% 7% 12% 6% 5% 6% 4 5% 6% 17%	2414
June	1st to 10th	Night	15% 11% 4 9% 6% 5% 6% 3 8% 7% 27%	1154
	11th to 20th	Night	17% 11% 4 10% 7% 7% 7% 4 7% 9% 18%	1140
	21st to end	Night	11% 6% 3 9% 7% 5% 6% 5% 7% 9% 30%	1140
July	1st to 10th	Night	13% 6% 2 5% 3 3 5% 3 5% 8% 47%	1900
	11th to 20th	Night	8% 5% 2 4 4 3 4 4 6% 6% 53%	1959
	21st to end	Night	10% 7% 3 7% 6% 5% 5% 5% 6% 9% 38%	2725
August	1st to 10th	Night	11% 8% 3 7% 5% 4 6% 5% 7% 10% 35%	2529
	11th to 20th	Night	12% 6% 2 7% 5% 6% 6% 5% 8% 9% 33%	2497
	21st to end	Night	13% 9% 3 8% 5% 5% 5% 5% 6% 8% 34%	3218
September	1st to 10th	Night	13% 9% 3 7% 4 4 5% 3 6% 7% 40%	1900
	11th to 20th	Night	11% 11% 3 8% 5% 4 6% 3 5% 6% 37%	1966
	21st to end	Night	9% 12% 4 10% 5% 5% 5% 5% 6% 8% 31%	2090
October	1st to 10th	Night	4 13% 6% 15% 9% 7% 6% 5% 5% 8% 23%	3731
	11th to 20th	Night	5% 11% 5% 14% 8% 7% 6% 5% 7% 8% 24%	4037
	21st to end	Night	4 12% 6% 14% 8% 8% 6% 5% 6% 6% 25%	4457
November	1st to 10th	Night	5% 16% 7% 14% 10% 9% 6% 6% 7% 7% 14%	2647
	11th to 20th	Night	2 13% 6% 13% 9% 8% 8% 6% 7% 8% 19%	2984
	21st to end	Night	2 12% 6% 14% 10% 9% 8% 6% 8% 7% 19%	3000
December	1st to 10th	Night	3 12% 5% 13% 10% 7% 7% 6% 8% 9% 21%	2878
	11th to 20th	Night	1 9% 7% 15% 10% 9% 8% 6% 10% 9% 15%	3702
	21st to end	Night	1 10% 6% 14% 7% 7% 8% 6% 8% 10% 25%	5566

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	70% 11% 11% 5% 2 1	1899
	11th to 20th	Day	58% 7% 8% 7% 12% 8%	2270
	21st to end	Day	69% 11% 11% 5% 4	2794
February	1st to 10th	Day	66% 9% 9% 7% 7% 2	1520
	11th to 20th	Day	67% 8% 8% 10% 5% 1	1570
	21st to end	Day	65% 8% 10% 10% 5% 2	1565
March	1st to 10th	Day	64% 10% 9% 8% 8%	3138
	11th to 20th	Day	58% 10% 10% 17% 4	3251
	21st to end	Day	66% 9% 11% 7% 6% 1	4165
April	1st to 10th	Day	77% 9% 8% 5% 1	2280
	11th to 20th	Day	69% 9% 12% 8% 2	2379
	21st to end	Day	68% 10% 10% 10% 2	2603
May	1st to 10th	Day	62% 8% 12% 13% 4	4420
	11th to 20th	Day	59% 12% 13% 12% 4	4586
	21st to end	Day	72% 10% 10% 6% 2	5162
June	1st to 10th	Day	65% 9% 11% 10% 4 1	3022
	11th to 20th	Day	72% 10% 10% 6% 2	3040
	21st to end	Day	62% 10% 13% 11% 4 1	3040
July	1st to 10th	Day	47% 9% 9% 16% 15% 5%	4981
	11th to 20th	Day	40% 9% 13% 22% 16% 1	4912
	21st to end	Day	50% 10% 11% 14% 11% 4	4671
August	1st to 10th	Day	44% 11% 12% 24% 8%	4384
	11th to 20th	Day	50% 12% 15% 18% 5%	4372
	21st to end	Day	54% 9% 14% 19% 4	4447
September	1st to 10th	Day	55% 8% 13% 19% 5% 1	2280
	11th to 20th	Day	53% 8% 14% 15% 9%	2214
	21st to end	Day	59% 9% 13% 12% 6% 1	2090
October	1st to 10th	Day	57% 12% 16% 11% 3	3247
	11th to 20th	Day	61% 10% 15% 13% 1	2891
	21st to end	Day	58% 11% 17% 11% 3	3101
November	1st to 10th	Day	69% 12% 8% 7% 3 1	1644
	11th to 20th	Day	58% 14% 13% 8% 6% 1	1400
	21st to end	Day	61% 13% 12% 6% 4 4	1400
December	1st to 10th	Day	65% 8% 7% 12% 6% 1	1337
	11th to 20th	Day	65% 9% 10% 9% 5% 2	1487
	21st to end	Day	54% 10% 13% 12% 10%	2090
January	1st to 10th	Night	72% 10% 8% 5% 3 1	5046
	11th to 20th	Night	56% 8% 7% 9% 16% 5%	4707
	21st to end	Night	73% 8% 7% 7% 3 1	4862
February	1st to 10th	Night	70% 8% 7% 7% 6% 2	2660
	11th to 20th	Night	66% 10% 9% 8% 6% 1	2504
	21st to end	Night	60% 9% 10% 13% 6% 2	1889
March	1st to 10th	Night	58% 13% 12% 8% 8% 1	3736
	11th to 20th	Night	55% 10% 14% 17% 3	3729
	21st to end	Night	62% 11% 12% 9% 7%	3488
April	1st to 10th	Night	68% 11% 11% 9% 1	1900
	11th to 20th	Night	58% 10% 15% 12% 5%	1751
	21st to end	Night	58% 11% 12% 15% 4	1575
May	1st to 10th	Night	55% 12% 14% 16% 3	2540
	11th to 20th	Night	54% 13% 13% 13% 6%	2309
	21st to end	Night	66% 11% 10% 9% 3	2414
June	1st to 10th	Night	55% 11% 17% 11% 6% 1	1154
	11th to 20th	Night	62% 14% 13% 9% 3	1140
	21st to end	Night	49% 14% 20% 12% 4 1	1140
July	1st to 10th	Night	38% 8% 13% 20% 19% 2	1870
	11th to 20th	Night	31% 8% 13% 25% 23%	1923
	21st to end	Night	43% 9% 14% 21% 9% 5%	2639
August	1st to 10th	Night	39% 13% 17% 28% 3	2521
	11th to 20th	Night	43% 14% 21% 18% 4	2521
	21st to end	Night	48% 10% 22% 16% 4	3218
September	1st to 10th	Night	45% 9% 17% 21% 6% 1	1900
	11th to 20th	Night	48% 9% 16% 18% 8%	1966
	21st to end	Night	51% 13% 15% 15% 6% 1	2090
October	1st to 10th	Night	59% 14% 15% 10% 2	3731
	11th to 20th	Night	57% 10% 18% 12% 2	4037
	21st to end	Night	59% 12% 19% 7% 3	4457
November	1st to 10th	Night	70% 12% 9% 5% 3 1	2647
	11th to 20th	Night	64% 13% 10% 7% 5% 1	2984
	21st to end	Night	64% 12% 10% 8% 4 3	3000
December	1st to 10th	Night	63% 10% 8% 9% 9% 1	2878
	11th to 20th	Night	68% 10% 10% 7% 4	3699
	21st to end	Night	54% 12% 13% 13% 6% 1	5566

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	8% 14% 36% 32% 6% 3	180
	11th to 20th	Day	10% 14% 39% 28% 6% 3	180
	21st to end	Day	16% 16% 35% 24% 6% 3	198
February	1st to 10th	Day	18% 21% 36% 18% 6% 2	180
	11th to 20th	Day	13% 19% 36% 21% 9% 2	262
	21st to end	Day	13% 21% 40% 17% 9% 1	379
March	1st to 10th	Day	15% 26% 31% 17% 10% 1	460
	11th to 20th	Day	14% 25% 36% 16% 7% 2	460
	21st to end	Day	16% 23% 32% 19% 8% 2	506
April	1st to 10th	Day	21% 23% 32% 17% 5% 1	460
	11th to 20th	Day	15% 20% 30% 23% 8% 3	452
	21st to end	Day	21% 22% 27% 19% 8% 3	460
May	1st to 10th	Day	22% 17% 29% 23% 8% 1	463
	11th to 20th	Day	18% 12% 25% 29% 13% 3	602
	21st to end	Day	20% 13% 23% 24% 16% 3	734
June	1st to 10th	Day	21% 18% 32% 21% 7% 1	852
	11th to 20th	Day	26% 15% 29% 20% 9% 1	870
	21st to end	Day	18% 13% 29% 25% 13% 2	870
July	1st to 10th	Day	19% 11% 28% 27% 13% 1	856
	11th to 20th	Day	17% 13% 33% 25% 10% 1	817
	21st to end	Day	16% 16% 30% 23% 13% 3	552
August	1st to 10th	Day	19% 10% 28% 28% 11% 4	487
	11th to 20th	Day	15% 19% 37% 17% 10% 2	477
	21st to end	Day	22% 16% 33% 19% 9% 1	539
September	1st to 10th	Day	23% 19% 28% 20% 8% 1	490
	11th to 20th	Day	17% 19% 31% 24% 7% 2	490
	21st to end	Day	31% 23% 24% 16% 4 1	490
October	1st to 10th	Day	24% 21% 28% 16% 9% 2	490
	11th to 20th	Day	24% 20% 28% 20% 7% 1	336
	21st to end	Day	18% 17% 39% 20% 5% 1	330
November	1st to 10th	Day	22% 23% 37% 12% 5% 2	243
	11th to 20th	Day	18% 21% 34% 21% 5% 2	200
	21st to end	Day	16% 23% 28% 22% 9% 3	200
December	1st to 10th	Day	9% 19% 34% 24% 7% 7%	182
	11th to 20th	Day	10% 13% 44% 23% 7% 2	180
	21st to end	Day	8% 14% 36% 27% 13% 3	198
January	1st to 10th	Night	10% 16% 47% 21% 5% 1	1040
	11th to 20th	Night	9% 16% 49% 19% 6% 1	882
	21st to end	Night	10% 19% 46% 18% 6% 1	836
February	1st to 10th	Night	12% 16% 39% 23% 8% 1	760
	11th to 20th	Night	8% 13% 44% 27% 7% 1	744
	21st to end	Night	8% 13% 40% 27% 10% 2	628
March	1st to 10th	Night	6% 16% 42% 26% 9% 1	760
	11th to 20th	Night	5% 17% 46% 24% 8% 1	760
	21st to end	Night	6% 12% 39% 30% 11% 2	836
April	1st to 10th	Night	8% 15% 34% 33% 10% 1	760
	11th to 20th	Night	8% 13% 37% 27% 14%	623
	21st to end	Night	14% 13% 31% 31% 10% 1	435
May	1st to 10th	Night	12% 10% 24% 41% 14%	380
	11th to 20th	Night	9% 6% 25% 39% 20% 1	374
	21st to end	Night	17% 9% 27% 25% 21% 1	411
June	1st to 10th	Night	17% 6% 34% 27% 15% 1	380
	11th to 20th	Night	19% 9% 29% 28% 14% 1	380
	21st to end	Night	12% 8% 27% 33% 19% 1	380
July	1st to 10th	Night	16% 4 25% 37% 17% 1	370
	11th to 20th	Night	16% 9% 23% 35% 17%	368
	21st to end	Night	9% 8% 21% 40% 21%	416
August	1st to 10th	Night	13% 4 18% 40% 23% 2	378
	11th to 20th	Night	14% 5% 23% 37% 20% 1	376
	21st to end	Night	17% 8% 30% 34% 10% 1	660
September	1st to 10th	Night	17% 9% 30% 31% 13% 1	760
	11th to 20th	Night	16% 9% 28% 29% 16% 2	760
	21st to end	Night	19% 15% 33% 22% 10% 1	760
October	1st to 10th	Night	15% 13% 33% 28% 9% 1	760
	11th to 20th	Night	14% 16% 38% 26% 5% 1	760
	21st to end	Night	14% 16% 44% 22% 4	836
November	1st to 10th	Night	14% 18% 45% 18% 5% 1	780
	11th to 20th	Night	12% 19% 48% 17% 3	984
	21st to end	Night	10% 15% 51% 17% 5% 2	1000
December	1st to 10th	Night	9% 18% 45% 20% 8% 1	960
	11th to 20th	Night	8% 14% 50% 20% 6% 1	1017
	21st to end	Night	5% 14% 50% 24% 7% 1	1144

Page generated at 2024-11-29 08:43:05. Version ac07

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