Nordegg
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Nordegg 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% 10% 4 10% 6% 5% 5% 4 6% 8% 33%	112922
	Night	6% 10% 4 10% 6% 5% 5% 4 6% 8% 34%	114386
Transparency	Day	48% 4 14% 22% 11% 2	112666
	Night	47% 4 15% 23% 10% 1	114288
Seeing	Day	18% 17% 30% 23% 10% 2	16100
	Night	13% 13% 33% 28% 12% 1	24715

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	2 8% 5% 14% 7% 5% 5% 4 7% 9% 33%	3179
	11th to 20th	Day	2 10% 3 9% 6% 8% 6% 6% 6% 9% 34%	3296
	21st to end	Day	2 7% 4 11% 6% 6% 6% 5% 6% 10% 38%	4004
February	1st to 10th	Day	3 10% 6% 11% 8% 7% 6% 6% 8% 7% 29%	1600
	11th to 20th	Day	3 13% 5% 14% 6% 6% 5% 5% 6% 8% 30%	1644
	21st to end	Day	2 9% 5% 14% 9% 6% 8% 5% 6% 6% 30%	1611
March	1st to 10th	Day	1 6% 4 16% 8% 6% 5% 4 6% 10% 33%	3138
	11th to 20th	Day	3 10% 4 8% 5% 5% 5% 4 7% 9% 41%	3328
	21st to end	Day	3 17% 9% 20% 6% 4 4 4 5% 6% 23%	4055
April	1st to 10th	Day	5% 18% 5% 11% 8% 6% 6% 5% 7% 8% 21%	2280
	11th to 20th	Day	8% 19% 6% 12% 7% 5% 4 5% 5% 7% 22%	2438
	21st to end	Day	9% 17% 5% 13% 6% 6% 6% 4 5% 6% 24%	2517
May	1st to 10th	Day	16% 18% 4 9% 6% 5% 5% 3 5% 7% 23%	4435
	11th to 20th	Day	12% 12% 4 10% 7% 6% 6% 4 7% 7% 24%	4694
	21st to end	Day	18% 14% 5% 11% 7% 6% 6% 4 5% 5% 19%	5161
June	1st to 10th	Day	19% 10% 4 8% 5% 6% 6% 4 7% 7% 24%	2857
	11th to 20th	Day	21% 11% 3 9% 7% 5% 6% 5% 6% 7% 19%	3040
	21st to end	Day	12% 7% 3 9% 7% 6% 6% 4 8% 7% 31%	3040
July	1st to 10th	Day	10% 7% 3 7% 6% 5% 5% 4 5% 7% 41%	5043
	11th to 20th	Day	9% 4 2 6% 5% 4 6% 5% 7% 8% 45%	4740
	21st to end	Day	9% 7% 3 6% 5% 5% 5% 5% 7% 8% 40%	4959
August	1st to 10th	Day	14% 7% 2 6% 4 5% 5% 4 6% 8% 38%	4401
	11th to 20th	Day	12% 7% 3 8% 5% 6% 6% 5% 7% 8% 33%	4251
	21st to end	Day	13% 7% 3 7% 5% 5% 5% 4 6% 8% 38%	4521
September	1st to 10th	Day	13% 10% 3 6% 5% 4 4 4 5% 7% 38%	2294
	11th to 20th	Day	14% 9% 3 6% 5% 3 4 4 6% 8% 38%	2154
	21st to end	Day	11% 10% 3 7% 5% 4 5% 3 6% 8% 38%	2090
October	1st to 10th	Day	7% 11% 3 8% 4 5% 4 4 6% 8% 38%	3327
	11th to 20th	Day	7% 10% 4 9% 4 5% 5% 4 6% 9% 36%	2842
	21st to end	Day	6% 11% 4 9% 6% 5% 6% 4 6% 7% 38%	3101
November	1st to 10th	Day	5% 13% 6% 12% 7% 4 5% 4 7% 6% 31%	1652
	11th to 20th	Day	3 11% 4 10% 5% 6% 5% 4 6% 9% 36%	1400
	21st to end	Day	3 11% 5% 10% 7% 5% 5% 5% 7% 10% 33%	1400
December	1st to 10th	Day	6% 11% 6% 13% 7% 6% 6% 4 6% 7% 27%	2290
	11th to 20th	Day	2 8% 5% 12% 7% 6% 6% 5% 7% 8% 35%	2642
	21st to end	Day	1 10% 5% 11% 5% 5% 6% 4 5% 7% 41%	3498
January	1st to 10th	Night	1 9% 6% 16% 7% 7% 6% 5% 6% 7% 30%	6766
	11th to 20th	Night	1 8% 4 12% 8% 6% 6% 4 7% 8% 34%	6647
	21st to end	Night	2 9% 5% 13% 6% 5% 5% 4 7% 9% 36%	6952
February	1st to 10th	Night	3 12% 4 12% 10% 6% 6% 4 5% 7% 29%	2800
	11th to 20th	Night	3 13% 5% 12% 8% 6% 6% 4 6% 8% 28%	2639
	21st to end	Night	1 8% 5% 14% 9% 6% 6% 4 5% 6% 35%	1937
March	1st to 10th	Night	1 7% 4 13% 9% 8% 7% 5% 7% 9% 30%	3736
	11th to 20th	Night	4 8% 3 6% 5% 4 5% 5% 8% 10% 42%	3650
	21st to end	Night	3 19% 9% 17% 6% 4 4 3 5% 6% 25%	3595
April	1st to 10th	Night	5% 14% 5% 10% 6% 6% 6% 4 6% 8% 30%	1900
	11th to 20th	Night	7% 15% 5% 11% 7% 5% 4 4 5% 7% 30%	1692
	21st to end	Night	8% 16% 4 9% 5% 5% 6% 5% 6% 7% 31%	1662
May	1st to 10th	Night	14% 20% 5% 10% 5% 4 4 3 4 5% 25%	2523
	11th to 20th	Night	11% 12% 4 8% 6% 5% 6% 5% 8% 7% 29%	2199
	21st to end	Night	16% 12% 3 7% 5% 5% 6% 4 7% 8% 27%	2414
June	1st to 10th	Night	19% 9% 3 7% 5% 5% 4 4 6% 7% 33%	1319
	11th to 20th	Night	20% 9% 3 7% 5% 4 5% 5% 7% 7% 27%	1140
	21st to end	Night	11% 8% 2 8% 5% 4 4 5% 7% 7% 39%	1140
July	1st to 10th	Night	11% 9% 3 8% 5% 4 4 4 6% 7% 39%	1900
	11th to 20th	Night	7% 4 2 4 4 4 4 4 7% 9% 51%	2220
	21st to end	Night	7% 6% 2 5% 5% 4 4 4 5% 8% 49%	2591
August	1st to 10th	Night	14% 7% 2 7% 3 3 4 3 7% 8% 41%	2529
	11th to 20th	Night	13% 9% 3 6% 4 4 4 5% 7% 10% 35%	2579
	21st to end	Night	15% 9% 2 6% 4 3 3 3 5% 8% 42%	3146
September	1st to 10th	Night	12% 8% 3 7% 4 3 5% 5% 5% 6% 43%	1884
	11th to 20th	Night	14% 10% 3 6% 4 4 4 4 6% 7% 40%	2025
	21st to end	Night	9% 9% 3 6% 3 3 4 5% 7% 7% 43%	2090
October	1st to 10th	Night	7% 10% 4 7% 5% 5% 5% 5% 6% 8% 37%	3648
	11th to 20th	Night	7% 10% 3 9% 5% 4 4 4 7% 7% 39%	4086
	21st to end	Night	5% 12% 4 9% 5% 4 4 4 5% 7% 41%	4457
November	1st to 10th	Night	5% 14% 5% 12% 5% 4 5% 4 5% 7% 34%	2622
	11th to 20th	Night	3 12% 5% 9% 6% 6% 6% 5% 8% 8% 35%	3000
	21st to end	Night	4 11% 4 11% 8% 5% 5% 5% 6% 8% 32%	3000
December	1st to 10th	Night	3 11% 6% 11% 8% 7% 6% 5% 6% 7% 29%	4890
	11th to 20th	Night	1 10% 5% 13% 9% 8% 6% 5% 7% 8% 27%	5550
	21st to end	Night	1 12% 6% 12% 6% 5% 5% 4 6% 8% 35%	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	47% 3 12% 25% 11% 2	3179
	11th to 20th	Day	44% 3 14% 19% 16% 4	3317
	21st to end	Day	40% 4 19% 26% 10%	4004
February	1st to 10th	Day	51% 3 12% 17% 13% 4	1600
	11th to 20th	Day	52% 3 13% 19% 11% 2	1652
	21st to end	Day	52% 4 11% 17% 15% 2	1611
March	1st to 10th	Day	46% 2 14% 19% 17% 1	3138
	11th to 20th	Day	39% 2 16% 26% 16% 1	3329
	21st to end	Day	62% 2 9% 18% 6% 2	4055
April	1st to 10th	Day	60% 4 13% 16% 7% 1	2280
	11th to 20th	Day	61% 3 10% 18% 7% 1	2438
	21st to end	Day	60% 4 10% 18% 7% 1	2517
May	1st to 10th	Day	61% 2 9% 21% 6%	4435
	11th to 20th	Day	59% 2 10% 20% 9%	4698
	21st to end	Day	67% 2 11% 11% 9% 1	5162
June	1st to 10th	Day	57% 4 12% 18% 8% 1	2857
	11th to 20th	Day	61% 4 11% 15% 8% 1	3040
	21st to end	Day	48% 4 16% 20% 10% 1	3040
July	1st to 10th	Day	40% 5% 11% 20% 19% 6%	4964
	11th to 20th	Day	33% 7% 14% 29% 15% 3	4659
	21st to end	Day	37% 7% 14% 23% 17% 2	4802
August	1st to 10th	Day	41% 6% 14% 31% 8%	4384
	11th to 20th	Day	43% 7% 17% 23% 9% 1	4293
	21st to end	Day	41% 7% 18% 27% 7% 1	4520
September	1st to 10th	Day	46% 3 15% 23% 10% 2	2294
	11th to 20th	Day	45% 4 15% 26% 10% 2	2154
	21st to end	Day	44% 4 15% 21% 12% 3	2090
October	1st to 10th	Day	40% 7% 19% 26% 8% 1	3327
	11th to 20th	Day	44% 5% 16% 24% 10% 1	2842
	21st to end	Day	44% 5% 13% 30% 8% 1	3101
November	1st to 10th	Day	51% 4 15% 19% 10% 2	1652
	11th to 20th	Day	45% 4 17% 21% 12% 1	1400
	21st to end	Day	44% 4 19% 21% 8% 3	1400
December	1st to 10th	Day	55% 6% 16% 14% 7% 1	2290
	11th to 20th	Day	45% 4 19% 23% 8% 1	2644
	21st to end	Day	42% 4 10% 25% 16% 3	3498
January	1st to 10th	Night	53% 3 11% 22% 9% 2	6766
	11th to 20th	Night	45% 4 14% 16% 16% 4	6688
	21st to end	Night	44% 3 21% 21% 9% 1	6952
February	1st to 10th	Night	54% 3 11% 18% 12% 3	2800
	11th to 20th	Night	51% 3 13% 18% 12% 2	2641
	21st to end	Night	50% 2 9% 24% 13% 2	1937
March	1st to 10th	Night	51% 2 15% 18% 14% 1	3736
	11th to 20th	Night	37% 3 19% 25% 15% 1	3650
	21st to end	Night	61% 2 9% 19% 8% 1	3595
April	1st to 10th	Night	52% 4 13% 20% 10% 1	1900
	11th to 20th	Night	55% 2 13% 19% 10% 1	1692
	21st to end	Night	52% 4 12% 24% 7% 1	1662
May	1st to 10th	Night	62% 2 13% 20% 4	2523
	11th to 20th	Night	53% 2 8% 27% 10%	2199
	21st to end	Night	54% 2 13% 21% 10% 1	2414
June	1st to 10th	Night	49% 3 15% 22% 9% 2	1319
	11th to 20th	Night	53% 4 17% 19% 7%	1140
	21st to end	Night	41% 4 18% 27% 8% 1	1140
July	1st to 10th	Night	41% 6% 13% 24% 11% 6%	1870
	11th to 20th	Night	26% 6% 22% 30% 13% 4	2178
	21st to end	Night	32% 5% 16% 31% 14% 1	2509
August	1st to 10th	Night	38% 5% 16% 36% 5%	2521
	11th to 20th	Night	40% 7% 22% 24% 7%	2603
	21st to end	Night	40% 4 17% 30% 7% 1	3146
September	1st to 10th	Night	40% 3 16% 27% 11% 3	1884
	11th to 20th	Night	43% 3 15% 26% 10% 3	2025
	21st to end	Night	38% 3 18% 26% 12% 2	2090
October	1st to 10th	Night	40% 7% 18% 24% 9% 1	3648
	11th to 20th	Night	41% 4 15% 30% 10% 1	4086
	21st to end	Night	41% 5% 14% 30% 10%	4457
November	1st to 10th	Night	50% 3 12% 21% 12% 1	2622
	11th to 20th	Night	45% 4 17% 22% 12% 1	3000
	21st to end	Night	48% 4 15% 21% 9% 3	3000
December	1st to 10th	Night	51% 7% 16% 17% 8% 2	4890
	11th to 20th	Night	53% 5% 16% 16% 9% 1	5547
	21st to end	Night	47% 3 13% 23% 12% 3	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	7% 16% 31% 31% 11% 5%	200
	11th to 20th	Day	8% 17% 37% 27% 9% 3	200
	21st to end	Day	14% 19% 41% 19% 5% 2	220
February	1st to 10th	Day	16% 17% 37% 21% 7% 3	200
	11th to 20th	Day	7% 21% 37% 26% 9%	252
	21st to end	Day	9% 26% 32% 22% 9% 2	399
March	1st to 10th	Day	13% 24% 34% 19% 7% 2	460
	11th to 20th	Day	13% 21% 36% 20% 6% 3	460
	21st to end	Day	17% 25% 31% 18% 7% 1	506
April	1st to 10th	Day	22% 23% 31% 17% 6% 2	460
	11th to 20th	Day	19% 23% 26% 22% 8% 2	452
	21st to end	Day	20% 21% 29% 20% 8% 2	460
May	1st to 10th	Day	26% 17% 24% 23% 9%	465
	11th to 20th	Day	18% 13% 29% 25% 14% 2	675
	21st to end	Day	26% 12% 24% 23% 13% 3	734
June	1st to 10th	Day	23% 17% 29% 21% 10% 1	687
	11th to 20th	Day	27% 15% 26% 22% 9% 2	870
	21st to end	Day	17% 12% 27% 25% 16% 3	870
July	1st to 10th	Day	17% 10% 29% 29% 12% 3	852
	11th to 20th	Day	15% 11% 28% 27% 17% 2	668
	21st to end	Day	14% 13% 28% 28% 14% 3	635
August	1st to 10th	Day	17% 14% 26% 29% 10% 4	487
	11th to 20th	Day	14% 16% 30% 27% 10% 3	477
	21st to end	Day	18% 15% 30% 23% 11% 3	539
September	1st to 10th	Day	22% 20% 27% 22% 9% 1	490
	11th to 20th	Day	21% 17% 29% 22% 8% 3	490
	21st to end	Day	21% 22% 30% 18% 8% 2	490
October	1st to 10th	Day	20% 17% 29% 19% 12% 3	467
	11th to 20th	Day	18% 18% 35% 17% 11% 2	300
	21st to end	Day	21% 16% 34% 18% 9% 1	330
November	1st to 10th	Day	19% 27% 28% 19% 5% 2	285
	11th to 20th	Day	17% 24% 33% 20% 6% 1	200
	21st to end	Day	8% 29% 28% 25% 8% 3	200
December	1st to 10th	Day	12% 23% 33% 19% 10% 4	200
	11th to 20th	Day	10% 20% 39% 23% 9% 1	200
	21st to end	Day	7% 16% 38% 27% 10% 1	220
January	1st to 10th	Night	11% 16% 37% 27% 7% 1	1000
	11th to 20th	Night	10% 18% 41% 23% 6% 1	960
	21st to end	Night	13% 21% 38% 21% 7% 1	880
February	1st to 10th	Night	12% 17% 31% 26% 12% 2	800
	11th to 20th	Night	11% 14% 38% 27% 9%	784
	21st to end	Night	6% 12% 38% 28% 13% 2	646
March	1st to 10th	Night	7% 16% 35% 28% 12% 2	760
	11th to 20th	Night	9% 14% 38% 28% 9% 1	760
	21st to end	Night	11% 13% 32% 31% 11% 2	836
April	1st to 10th	Night	14% 15% 28% 28% 13% 1	760
	11th to 20th	Night	17% 13% 32% 27% 10%	564
	21st to end	Night	20% 14% 27% 27% 11%	522
May	1st to 10th	Night	21% 9% 24% 29% 14% 1	380
	11th to 20th	Night	14% 8% 24% 38% 15% 1	374
	21st to end	Night	23% 5% 24% 27% 20% 1	411
June	1st to 10th	Night	24% 9% 26% 23% 16% 2	380
	11th to 20th	Night	23% 6% 22% 31% 16% 2	380
	21st to end	Night	13% 6% 23% 31% 24% 2	380
July	1st to 10th	Night	16% 4 21% 37% 22%	370
	11th to 20th	Night	15% 5% 27% 32% 21%	368
	21st to end	Night	11% 6% 17% 38% 25% 3	416
August	1st to 10th	Night	18% 2 15% 32% 29% 3	378
	11th to 20th	Night	13% 6% 18% 37% 25% 1	419
	21st to end	Night	15% 8% 22% 35% 19% 1	627
September	1st to 10th	Night	16% 8% 25% 33% 16% 1	744
	11th to 20th	Night	20% 7% 22% 31% 18% 2	760
	21st to end	Night	15% 12% 31% 27% 12% 1	760
October	1st to 10th	Night	18% 10% 28% 31% 12% 1	760
	11th to 20th	Night	16% 13% 32% 30% 8% 1	760
	21st to end	Night	16% 13% 36% 27% 6% 2	836
November	1st to 10th	Night	15% 16% 36% 25% 8% 1	840
	11th to 20th	Night	12% 21% 41% 21% 5% 1	1000
	21st to end	Night	11% 19% 38% 24% 8% 1	1000
December	1st to 10th	Night	11% 18% 41% 21% 9% 1	1000
	11th to 20th	Night	7% 18% 39% 26% 9% 1	1000
	21st to end	Night	8% 15% 42% 24% 9% 1	1100

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