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 2024-09-29.

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% 32%	102353
	Night	6% 11% 4 10% 6% 5% 5% 4 6% 8% 35%	95929
Transparency	Day	49% 4 13% 21% 11% 2	102097
	Night	47% 3 15% 23% 10% 2	95831
Seeing	Day	18% 17% 29% 23% 10% 2	15738
	Night	13% 13% 32% 28% 12% 1	24049

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 7% 5% 14% 9% 6% 5% 4 8% 8% 31%	2219
	11th to 20th	Day	2 9% 3 10% 7% 5% 5% 7% 6% 9% 36%	2294
	21st to end	Day	2 9% 4 9% 6% 5% 6% 5% 7% 9% 38%	2794
February	1st to 10th	Day	4 10% 6% 11% 8% 7% 6% 5% 7% 7% 29%	1520
	11th to 20th	Day	3 14% 5% 14% 6% 6% 5% 5% 5% 8% 29%	1559
	21st to end	Day	2 9% 5% 14% 9% 6% 8% 4 6% 6% 30%	1570
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% 9% 3 7% 5% 4 5% 3 6% 8% 38%	2069
October	1st to 10th	Day	10% 12% 4 9% 4 5% 4 5% 5% 7% 36%	1897
	11th to 20th	Day	9% 11% 4 9% 4 5% 5% 3 5% 7% 39%	1620
	21st to end	Day	6% 13% 5% 11% 7% 5% 5% 3 5% 7% 32%	1782
November	1st to 10th	Day	5% 13% 6% 11% 7% 4 5% 4 7% 6% 31%	1569
	11th to 20th	Day	4 11% 5% 10% 5% 5% 5% 4 6% 9% 37%	1330
	21st to end	Day	3 10% 5% 9% 7% 5% 4 5% 7% 10% 34%	1330
December	1st to 10th	Day	4 11% 5% 14% 7% 6% 6% 4 6% 7% 32%	1330
	11th to 20th	Day	2 9% 5% 13% 7% 6% 6% 5% 7% 7% 34%	1682
	21st to end	Day	2 11% 4 10% 5% 4 5% 5% 5% 7% 42%	2442
January	1st to 10th	Night	1 9% 6% 16% 7% 6% 5% 5% 7% 8% 30%	4726
	11th to 20th	Night	2 8% 4 11% 7% 6% 5% 5% 8% 8% 35%	4635
	21st to end	Night	3 11% 4 11% 6% 6% 6% 4 7% 9% 33%	4862
February	1st to 10th	Night	3 13% 4 13% 9% 6% 5% 4 5% 7% 30%	2660
	11th to 20th	Night	3 13% 5% 12% 7% 6% 6% 4 7% 8% 28%	2504
	21st to end	Night	1 8% 5% 14% 9% 6% 6% 5% 5% 6% 35%	1884
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 4 4 5% 7% 7% 43%	2079
October	1st to 10th	Night	10% 12% 4 7% 4 4 4 3 5% 7% 41%	2060
	11th to 20th	Night	8% 11% 3 8% 5% 5% 4 4 6% 6% 39%	2340
	21st to end	Night	5% 13% 5% 11% 5% 5% 5% 4 6% 7% 33%	2574
November	1st to 10th	Night	5% 14% 5% 12% 5% 4 5% 4 5% 7% 34%	2487
	11th to 20th	Night	3 12% 5% 9% 6% 6% 6% 5% 7% 8% 35%	2850
	21st to end	Night	4 11% 4 11% 8% 5% 5% 5% 6% 8% 32%	2850
December	1st to 10th	Night	4 13% 5% 10% 7% 5% 6% 4 6% 7% 34%	2850
	11th to 20th	Night	2 10% 6% 12% 8% 8% 6% 5% 7% 8% 29%	3510
	21st to end	Night	1 11% 5% 12% 5% 5% 5% 4 6% 7% 38%	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	49% 2 11% 25% 10% 2	2219
	11th to 20th	Day	44% 2 12% 18% 20% 4	2315
	21st to end	Day	42% 3 19% 28% 8% 1	2794
February	1st to 10th	Day	52% 2 12% 18% 12% 4	1520
	11th to 20th	Day	53% 3 12% 19% 10% 2	1567
	21st to end	Day	53% 3 11% 17% 15% 1	1570
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	2069
October	1st to 10th	Day	47% 4 13% 25% 10% 1	1897
	11th to 20th	Day	46% 3 16% 24% 10% 1	1620
	21st to end	Day	52% 4 12% 20% 11% 1	1782
November	1st to 10th	Day	51% 4 15% 19% 10% 2	1569
	11th to 20th	Day	45% 3 17% 21% 12% 1	1330
	21st to end	Day	43% 4 20% 21% 8% 3	1330
December	1st to 10th	Day	53% 4 13% 16% 12% 2	1330
	11th to 20th	Day	49% 3 15% 22% 10% 2	1684
	21st to end	Day	42% 2 10% 24% 17% 5%	2442
January	1st to 10th	Night	52% 2 11% 21% 11% 2	4726
	11th to 20th	Night	46% 3 13% 16% 17% 6%	4676
	21st to end	Night	48% 2 19% 22% 9% 1	4862
February	1st to 10th	Night	54% 3 11% 19% 11% 3	2660
	11th to 20th	Night	51% 3 14% 18% 12% 2	2506
	21st to end	Night	50% 2 9% 24% 13% 2	1884
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	39% 3 18% 26% 13% 2	2079
October	1st to 10th	Night	43% 3 15% 27% 10% 1	2060
	11th to 20th	Night	45% 3 17% 24% 11% 1	2340
	21st to end	Night	49% 5% 13% 23% 10%	2574
November	1st to 10th	Night	50% 3 12% 21% 12% 1	2487
	11th to 20th	Night	45% 4 17% 22% 11% 1	2850
	21st to end	Night	48% 4 15% 21% 10% 3	2850
December	1st to 10th	Night	49% 4 10% 22% 12% 3	2850
	11th to 20th	Night	51% 4 17% 20% 7% 1	3507
	21st to end	Night	45% 2 14% 23% 12% 4	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	7% 17% 28% 32% 12% 4	180
	11th to 20th	Day	8% 14% 37% 28% 10% 3	180
	21st to end	Day	14% 19% 38% 21% 6% 2	198
February	1st to 10th	Day	17% 18% 36% 20% 6% 3	180
	11th to 20th	Day	8% 22% 36% 26% 9%	227
	21st to end	Day	9% 24% 33% 23% 9% 2	382
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	20% 22% 30% 18% 8% 2	483
October	1st to 10th	Day	20% 17% 29% 19% 12% 3	429
	11th to 20th	Day	17% 17% 34% 19% 11% 2	270
	21st to end	Day	22% 15% 34% 19% 8% 1	297
November	1st to 10th	Day	19% 26% 28% 19% 5% 2	257
	11th to 20th	Day	16% 23% 34% 21% 5% 1	180
	21st to end	Day	8% 31% 27% 23% 8% 3	180
December	1st to 10th	Day	12% 22% 32% 19% 11% 4	180
	11th to 20th	Day	10% 21% 38% 22% 8% 1	180
	21st to end	Day	7% 16% 38% 28% 11% 1	198
January	1st to 10th	Night	12% 16% 38% 27% 7% 1	950
	11th to 20th	Night	10% 17% 41% 24% 7% 1	912
	21st to end	Night	12% 20% 38% 22% 8% 1	836
February	1st to 10th	Night	12% 17% 31% 26% 12% 2	760
	11th to 20th	Night	12% 14% 38% 26% 10%	744
	21st to end	Night	5% 12% 38% 29% 14% 2	628
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	756
October	1st to 10th	Night	18% 9% 26% 33% 13% 1	720
	11th to 20th	Night	16% 13% 31% 30% 8% 2	720
	21st to end	Night	16% 13% 36% 27% 6% 2	792
November	1st to 10th	Night	15% 15% 36% 25% 8% 1	797
	11th to 20th	Night	12% 21% 41% 21% 5% 1	950
	21st to end	Night	11% 20% 37% 23% 8% 1	950
December	1st to 10th	Night	11% 17% 40% 21% 10% 1	950
	11th to 20th	Night	7% 18% 39% 26% 9% 1	950
	21st to end	Night	8% 15% 42% 24% 9% 1	1045

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