Peyto Lake
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Peyto Lake 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	6% 17% 6% 13% 7% 5% 5% 4 5% 6% 25%	106128
	Night	4 15% 7% 15% 8% 6% 5% 4 6% 6% 24%	101429
Transparency	Day	57% 7% 12% 16% 7% 1	105882
	Night	58% 6% 12% 15% 7% 1	101322
Seeing	Day	16% 15% 28% 24% 13% 4	15669
	Night	11% 10% 28% 33% 15% 3	24147

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 12% 10% 26% 13% 11% 7% 3 4 6% 8%	2219
	11th to 20th	Day	1 15% 8% 17% 7% 4 4 4 5% 5% 29%	2388
	21st to end	Day	1 22% 10% 23% 8% 6% 5% 4 4 5% 12%	2794
February	1st to 10th	Day	2 16% 9% 21% 9% 8% 6% 4 5% 5% 15%	1520
	11th to 20th	Day	1 14% 9% 22% 11% 7% 6% 4 4 7% 16%	1593
	21st to end	Day	1 10% 10% 22% 12% 10% 6% 4 5% 5% 15%	1570
March	1st to 10th	Day	12% 9% 23% 15% 7% 6% 4 4 5% 15%	3138
	11th to 20th	Day	1 15% 8% 21% 7% 5% 4 3 4 5% 27%	3303
	21st to end	Day	1 18% 12% 22% 10% 5% 4 3 4 5% 15%	4072
April	1st to 10th	Day	4 18% 11% 24% 10% 5% 4 4 4 5% 10%	2280
	11th to 20th	Day	4 24% 10% 15% 8% 6% 5% 3 5% 5% 15%	2411
	21st to end	Day	6% 24% 9% 15% 7% 6% 4 3 5% 6% 15%	2513
May	1st to 10th	Day	8% 23% 7% 11% 6% 5% 4 4 5% 6% 21%	4420
	11th to 20th	Day	6% 20% 6% 11% 6% 5% 5% 4 7% 7% 22%	4616
	21st to end	Day	10% 27% 8% 13% 5% 4 4 3 4 5% 16%	5161
June	1st to 10th	Day	14% 17% 4 9% 6% 6% 5% 4 6% 6% 22%	2850
	11th to 20th	Day	14% 19% 4 10% 7% 5% 5% 5% 6% 7% 20%	2978
	21st to end	Day	11% 11% 3 9% 5% 6% 6% 5% 7% 8% 29%	3040
July	1st to 10th	Day	6% 9% 3 6% 5% 5% 5% 4 5% 5% 47%	4944
	11th to 20th	Day	7% 6% 2 6% 4 4 5% 4 6% 7% 51%	4740
	21st to end	Day	7% 9% 3 8% 5% 5% 4 5% 7% 8% 40%	4853
August	1st to 10th	Day	9% 8% 2 7% 6% 5% 6% 5% 7% 8% 38%	4401
	11th to 20th	Day	11% 8% 3 8% 6% 6% 6% 5% 6% 8% 33%	4250
	21st to end	Day	12% 15% 4 8% 5% 5% 5% 4 6% 7% 30%	4477
September	1st to 10th	Day	11% 15% 4 8% 5% 4 5% 4 5% 7% 34%	2280
	11th to 20th	Day	11% 18% 4 8% 4 4 4 4 4 6% 33%	2163
	21st to end	Day	11% 22% 5% 8% 5% 4 4 3 5% 5% 28%	2090
October	1st to 10th	Day	8% 26% 6% 9% 5% 4 4 3 5% 7% 23%	3353
	11th to 20th	Day	9% 24% 6% 12% 4 4 4 3 6% 7% 20%	2842
	21st to end	Day	3 20% 10% 17% 5% 4 4 3 4 5% 25%	3101
November	1st to 10th	Day	5% 22% 10% 20% 8% 6% 4 3 4 4 14%	1654
	11th to 20th	Day	1 18% 7% 18% 9% 7% 5% 5% 6% 5% 18%	1330
	21st to end	Day	2 16% 7% 19% 11% 7% 5% 4 5% 6% 19%	1330
December	1st to 10th	Day	2 15% 7% 16% 11% 7% 7% 4 5% 5% 20%	1330
	11th to 20th	Day	1 22% 9% 20% 8% 7% 5% 3 6% 6% 13%	1682
	21st to end	Day	1 18% 9% 14% 8% 6% 5% 4 5% 6% 25%	2442
January	1st to 10th	Night	1 12% 9% 32% 13% 8% 8% 3 3 3 8%	4726
	11th to 20th	Night	1 10% 7% 16% 10% 8% 6% 3 7% 8% 25%	4538
	21st to end	Night	1 26% 13% 18% 8% 6% 4 3 4 4 12%	4862
February	1st to 10th	Night	1 14% 9% 21% 12% 6% 7% 4 4 4 16%	2660
	11th to 20th	Night	2 14% 7% 21% 11% 6% 6% 4 5% 6% 18%	2471
	21st to end	Night	10% 10% 19% 11% 10% 6% 4 6% 6% 18%	1884
March	1st to 10th	Night	10% 6% 20% 13% 11% 7% 5% 7% 6% 14%	3736
	11th to 20th	Night	2 13% 9% 17% 7% 4 4 4 6% 8% 26%	3676
	21st to end	Night	1 13% 12% 24% 8% 6% 5% 5% 6% 5% 16%	3568
April	1st to 10th	Night	3 18% 9% 18% 8% 6% 6% 5% 6% 5% 17%	1900
	11th to 20th	Night	3 17% 8% 15% 9% 6% 6% 4 7% 6% 20%	1719
	21st to end	Night	4 18% 7% 11% 8% 8% 6% 4 6% 6% 23%	1666
May	1st to 10th	Night	7% 20% 8% 13% 6% 4 4 4 4 6% 25%	2540
	11th to 20th	Night	6% 13% 6% 12% 7% 7% 5% 5% 7% 7% 24%	2277
	21st to end	Night	8% 23% 8% 12% 5% 5% 5% 4 6% 6% 18%	2414
June	1st to 10th	Night	16% 17% 5% 8% 4 4 3 3 5% 7% 30%	1330
	11th to 20th	Night	12% 16% 4 11% 7% 6% 7% 4 6% 6% 20%	1195
	21st to end	Night	7% 10% 2 7% 5% 6% 5% 5% 8% 9% 35%	1140
July	1st to 10th	Night	7% 7% 2 6% 4 3 4 3 5% 7% 51%	2013
	11th to 20th	Night	5% 6% 1 4 2 3 4 4 6% 8% 56%	2220
	21st to end	Night	6% 10% 2 5% 4 3 4 4 5% 8% 49%	2696
August	1st to 10th	Night	9% 7% 3 6% 5% 5% 5% 4 7% 8% 42%	2529
	11th to 20th	Night	10% 7% 3 5% 4 4 5% 5% 8% 9% 42%	2579
	21st to end	Night	11% 12% 3 8% 5% 4 4 4 6% 7% 36%	3177
September	1st to 10th	Night	7% 12% 4 9% 5% 4 4 3 4 7% 40%	1900
	11th to 20th	Night	12% 13% 4 9% 4 4 4 3 4 7% 36%	2016
	21st to end	Night	9% 18% 4 8% 4 4 4 4 6% 5% 33%	2090
October	1st to 10th	Night	7% 19% 5% 9% 4 5% 5% 4 6% 7% 29%	3614
	11th to 20th	Night	7% 22% 5% 13% 4 4 5% 3 5% 7% 25%	4086
	21st to end	Night	3 17% 8% 19% 5% 4 4 3 5% 7% 24%	4457
November	1st to 10th	Night	4 22% 9% 18% 8% 6% 6% 4 5% 5% 12%	2476
	11th to 20th	Night	1 18% 8% 21% 10% 7% 5% 4 4 5% 16%	2850
	21st to end	Night	2 18% 7% 21% 9% 7% 5% 3 5% 7% 16%	2850
December	1st to 10th	Night	2 13% 9% 17% 12% 7% 5% 4 4 5% 21%	2850
	11th to 20th	Night	1 16% 9% 20% 11% 11% 8% 4 6% 4 11%	3510
	21st to end	Night	1 15% 6% 17% 9% 7% 6% 5% 7% 8% 20%	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	75% 5% 8% 6% 3 1	2219
	11th to 20th	Day	55% 6% 9% 10% 11% 9%	2412
	21st to end	Day	70% 8% 11% 7% 4 1	2794
February	1st to 10th	Day	70% 5% 8% 7% 7% 3	1520
	11th to 20th	Day	68% 5% 8% 11% 6% 2	1601
	21st to end	Day	69% 6% 8% 10% 5% 2	1570
March	1st to 10th	Day	67% 6% 6% 11% 8% 1	3138
	11th to 20th	Day	56% 9% 14% 15% 6%	3304
	21st to end	Day	66% 10% 9% 8% 6% 2	4072
April	1st to 10th	Day	73% 8% 10% 7% 2	2280
	11th to 20th	Day	68% 8% 9% 11% 3 1	2411
	21st to end	Day	69% 9% 9% 11% 2 1	2513
May	1st to 10th	Day	61% 9% 10% 15% 4	4420
	11th to 20th	Day	53% 12% 13% 16% 5%	4620
	21st to end	Day	64% 12% 10% 10% 3	5162
June	1st to 10th	Day	59% 9% 13% 15% 3 1	2850
	11th to 20th	Day	61% 9% 13% 14% 4	2978
	21st to end	Day	50% 9% 17% 18% 6% 1	3040
July	1st to 10th	Day	39% 5% 9% 21% 23% 3	4868
	11th to 20th	Day	33% 5% 11% 29% 22% 1	4659
	21st to end	Day	42% 4 12% 25% 16% 1	4700
August	1st to 10th	Day	43% 5% 9% 32% 10%	4384
	11th to 20th	Day	48% 5% 16% 24% 7%	4292
	21st to end	Day	53% 4 18% 20% 5% 1	4476
September	1st to 10th	Day	48% 6% 17% 20% 8%	2280
	11th to 20th	Day	51% 7% 12% 20% 9%	2163
	21st to end	Day	58% 6% 13% 16% 7%	2090
October	1st to 10th	Day	62% 4 15% 14% 5%	3353
	11th to 20th	Day	63% 5% 14% 16% 2	2842
	21st to end	Day	62% 5% 11% 17% 5%	3101
November	1st to 10th	Day	72% 5% 9% 9% 3 2	1654
	11th to 20th	Day	64% 8% 12% 8% 7% 1	1330
	21st to end	Day	62% 8% 14% 9% 5% 2	1330
December	1st to 10th	Day	64% 5% 8% 15% 7% 1	1330
	11th to 20th	Day	70% 6% 9% 9% 5% 1	1684
	21st to end	Day	58% 5% 11% 13% 9% 3	2442
January	1st to 10th	Night	80% 4 6% 6% 3 1	4726
	11th to 20th	Night	56% 5% 7% 10% 14% 8%	4576
	21st to end	Night	74% 8% 7% 6% 4 1	4862
February	1st to 10th	Night	70% 5% 8% 9% 5% 3	2660
	11th to 20th	Night	65% 6% 10% 10% 7% 2	2473
	21st to end	Night	64% 4 9% 13% 7% 3	1884
March	1st to 10th	Night	59% 10% 8% 13% 8% 1	3736
	11th to 20th	Night	53% 8% 15% 17% 5% 1	3676
	21st to end	Night	66% 7% 10% 9% 6% 2	3568
April	1st to 10th	Night	65% 8% 13% 11% 3	1900
	11th to 20th	Night	58% 9% 13% 13% 6% 1	1719
	21st to end	Night	57% 9% 12% 16% 5% 1	1666
May	1st to 10th	Night	58% 7% 11% 19% 5%	2540
	11th to 20th	Night	51% 10% 14% 18% 6%	2277
	21st to end	Night	59% 10% 13% 15% 4	2414
June	1st to 10th	Night	53% 6% 14% 22% 4 1	1330
	11th to 20th	Night	59% 10% 11% 15% 5%	1195
	21st to end	Night	40% 7% 20% 26% 7% 1	1140
July	1st to 10th	Night	34% 4 9% 29% 22% 2	1980
	11th to 20th	Night	26% 4 13% 32% 23% 2	2178
	21st to end	Night	34% 3 14% 30% 18% 1	2611
August	1st to 10th	Night	38% 5% 13% 36% 8%	2521
	11th to 20th	Night	36% 4 26% 28% 5%	2603
	21st to end	Night	46% 4 25% 21% 5%	3177
September	1st to 10th	Night	42% 7% 17% 24% 10% 1	1900
	11th to 20th	Night	48% 6% 17% 19% 10% 1	2016
	21st to end	Night	49% 9% 15% 19% 8%	2090
October	1st to 10th	Night	54% 7% 18% 16% 5%	3614
	11th to 20th	Night	59% 4 14% 19% 4	4086
	21st to end	Night	60% 4 13% 17% 4	4457
November	1st to 10th	Night	72% 7% 7% 8% 5% 2	2476
	11th to 20th	Night	70% 6% 8% 8% 6% 2	2850
	21st to end	Night	67% 6% 11% 8% 5% 3	2850
December	1st to 10th	Night	65% 5% 7% 12% 9% 1	2850
	11th to 20th	Night	73% 7% 7% 7% 4 1	3507
	21st to end	Night	58% 7% 14% 10% 7% 2	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	4 25% 27% 26% 11% 7%	180
	11th to 20th	Day	8% 16% 37% 28% 9% 3	180
	21st to end	Day	6% 21% 39% 20% 11% 4	198
February	1st to 10th	Day	15% 20% 38% 18% 6% 4	180
	11th to 20th	Day	9% 21% 32% 25% 12% 1	261
	21st to end	Day	12% 17% 32% 27% 10% 2	382
March	1st to 10th	Day	11% 23% 35% 18% 9% 3	460
	11th to 20th	Day	10% 21% 37% 20% 9% 2	460
	21st to end	Day	12% 20% 33% 22% 9% 3	506
April	1st to 10th	Day	13% 23% 34% 20% 9% 1	460
	11th to 20th	Day	14% 21% 33% 19% 10% 3	452
	21st to end	Day	17% 19% 29% 20% 12% 3	460
May	1st to 10th	Day	19% 16% 28% 23% 11% 4	463
	11th to 20th	Day	13% 10% 20% 29% 21% 7%	623
	21st to end	Day	18% 10% 19% 27% 20% 7%	734
June	1st to 10th	Day	20% 12% 26% 24% 15% 3	680
	11th to 20th	Day	20% 11% 25% 26% 14% 4	808
	21st to end	Day	14% 8% 20% 30% 22% 7%	870
July	1st to 10th	Day	13% 8% 20% 30% 23% 6%	795
	11th to 20th	Day	15% 9% 22% 30% 19% 5%	668
	21st to end	Day	12% 10% 26% 27% 19% 6%	568
August	1st to 10th	Day	12% 9% 28% 28% 18% 4	487
	11th to 20th	Day	13% 13% 31% 28% 11% 3	477
	21st to end	Day	21% 14% 29% 23% 11% 2	539
September	1st to 10th	Day	20% 20% 27% 22% 9% 2	490
	11th to 20th	Day	22% 15% 26% 27% 7% 3	490
	21st to end	Day	28% 22% 26% 16% 7% 2	490
October	1st to 10th	Day	26% 14% 27% 20% 11% 3	490
	11th to 20th	Day	22% 21% 24% 22% 10% 1	300
	21st to end	Day	18% 16% 34% 23% 8% 2	330
November	1st to 10th	Day	16% 18% 37% 19% 9% 2	270
	11th to 20th	Day	16% 20% 42% 14% 7% 1	180
	21st to end	Day	12% 23% 30% 19% 8% 8%	180
December	1st to 10th	Day	9% 18% 25% 31% 6% 11%	180
	11th to 20th	Day	4 24% 37% 23% 11% 1	180
	21st to end	Day	8% 14% 28% 32% 16% 2	198
January	1st to 10th	Night	8% 16% 37% 31% 7% 1	950
	11th to 20th	Night	8% 12% 37% 33% 8% 2	851
	21st to end	Night	6% 15% 36% 31% 9% 3	836
February	1st to 10th	Night	7% 13% 34% 27% 13% 6%	760
	11th to 20th	Night	7% 11% 32% 35% 13% 2	744
	21st to end	Night	5% 10% 26% 37% 17% 4	628
March	1st to 10th	Night	5% 12% 37% 30% 14% 2	760
	11th to 20th	Night	7% 14% 30% 34% 13% 2	760
	21st to end	Night	7% 10% 28% 33% 18% 4	836
April	1st to 10th	Night	9% 11% 29% 31% 17% 3	760
	11th to 20th	Night	7% 12% 31% 35% 14% 2	591
	21st to end	Night	12% 9% 25% 35% 16% 2	526
May	1st to 10th	Night	14% 6% 18% 36% 21% 3	380
	11th to 20th	Night	11% 4 17% 36% 28% 5%	374
	21st to end	Night	18% 9% 13% 28% 28% 5%	411
June	1st to 10th	Night	24% 5% 14% 33% 18% 5%	380
	11th to 20th	Night	20% 5% 19% 32% 20% 3	380
	21st to end	Night	11% 4 14% 33% 32% 7%	380
July	1st to 10th	Night	12% 3 11% 40% 31% 4	370
	11th to 20th	Night	15% 4 12% 38% 29% 3	368
	21st to end	Night	6% 3 15% 39% 34% 4	416
August	1st to 10th	Night	9% 3 8% 35% 40% 5%	378
	11th to 20th	Night	13% 6% 12% 37% 28% 4	419
	21st to end	Night	14% 6% 17% 39% 21% 2	645
September	1st to 10th	Night	15% 6% 18% 34% 23% 5%	760
	11th to 20th	Night	17% 5% 15% 34% 22% 6%	760
	21st to end	Night	20% 11% 21% 31% 14% 4	760
October	1st to 10th	Night	16% 8% 21% 35% 16% 4	760
	11th to 20th	Night	16% 9% 26% 35% 11% 3	760
	21st to end	Night	13% 13% 31% 31% 11% 1	836
November	1st to 10th	Night	14% 11% 38% 27% 9% 2	763
	11th to 20th	Night	11% 19% 37% 28% 5% 1	950
	21st to end	Night	10% 13% 37% 28% 8% 3	950
December	1st to 10th	Night	8% 12% 35% 31% 11% 3	950
	11th to 20th	Night	6% 11% 39% 32% 9% 3	950
	21st to end	Night	4 11% 39% 33% 10% 3	1045

Page generated at 2024-11-01 20:47:34. Version ac07

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