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 2024-04-03.

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	7% 16% 7% 12% 9% 4 5% 5% 5% 6% 23%	78733
	Night	4 14% 8% 14% 10% 5% 6% 5% 5% 6% 23%	81348
Transparency	Day	59% 8% 12% 14% 6% 1	78445
	Night	60% 7% 12% 14% 7% 2	81217
Seeing	Day	15% 15% 28% 25% 14% 4	14740
	Night	10% 10% 28% 33% 15% 3	23538

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 11% 10% 22% 16% 9% 8% 4 4 6% 8%	2219
	11th to 20th	Day	1 14% 9% 15% 9% 4 4 5% 5% 5% 29%	2388
	21st to end	Day	1 20% 11% 21% 10% 5% 6% 4 4 6% 12%	2794
February	1st to 10th	Day	3 13% 11% 19% 11% 6% 6% 5% 5% 5% 15%	1520
	11th to 20th	Day	2 12% 11% 19% 13% 6% 6% 5% 5% 7% 16%	1593
	21st to end	Day	1 8% 11% 19% 15% 8% 7% 5% 5% 5% 15%	1570
March	1st to 10th	Day	1 16% 10% 20% 13% 5% 7% 5% 4 5% 14%	1900
	11th to 20th	Day	2 18% 12% 18% 11% 4 5% 3 4 5% 18%	1975
	21st to end	Day	1 22% 13% 17% 12% 4 5% 5% 4 5% 11%	2451
April	1st to 10th	Day	5% 16% 11% 22% 12% 4 5% 4 4 5% 11%	2185
	11th to 20th	Day	5% 23% 11% 13% 9% 4 5% 4 5% 6% 15%	2282
	21st to end	Day	6% 22% 10% 13% 8% 4 5% 3 5% 7% 16%	2380
May	1st to 10th	Day	7% 26% 8% 10% 7% 4 4 5% 5% 6% 18%	2520
	11th to 20th	Day	8% 15% 6% 8% 7% 3 6% 5% 6% 8% 29%	2604
	21st to end	Day	15% 19% 5% 8% 6% 3 5% 4 5% 6% 24%	2917
June	1st to 10th	Day	16% 15% 5% 8% 8% 4 5% 5% 6% 7% 22%	2700
	11th to 20th	Day	16% 17% 4 8% 8% 3 5% 6% 6% 7% 20%	2821
	21st to end	Day	11% 10% 4 8% 6% 4 6% 6% 7% 8% 30%	2880
July	1st to 10th	Day	9% 9% 4 7% 6% 4 5% 6% 5% 7% 37%	2820
	11th to 20th	Day	11% 9% 3 7% 6% 3 6% 6% 6% 8% 35%	2700
	21st to end	Day	7% 7% 3 7% 6% 3 4 5% 6% 8% 43%	2776
August	1st to 10th	Day	11% 8% 3 6% 7% 4 5% 6% 6% 8% 37%	2507
	11th to 20th	Day	11% 7% 3 6% 6% 3 6% 5% 5% 9% 38%	2434
	21st to end	Day	13% 14% 4 7% 7% 3 4 5% 5% 6% 32%	2556
September	1st to 10th	Day	11% 15% 5% 7% 6% 3 5% 5% 5% 7% 32%	2160
	11th to 20th	Day	12% 17% 5% 7% 4 3 4 5% 4 6% 34%	2050
	21st to end	Day	12% 22% 5% 7% 6% 3 4 4 5% 5% 28%	1980
October	1st to 10th	Day	10% 19% 7% 9% 6% 3 5% 3 5% 6% 27%	1908
	11th to 20th	Day	8% 21% 7% 10% 7% 3 6% 5% 6% 7% 21%	1620
	21st to end	Day	5% 22% 9% 12% 8% 4 5% 5% 5% 7% 18%	1782
November	1st to 10th	Day	5% 20% 11% 19% 10% 5% 5% 4 4 5% 14%	1627
	11th to 20th	Day	1 16% 9% 15% 11% 5% 6% 6% 5% 6% 18%	1330
	21st to end	Day	2 14% 8% 17% 13% 5% 5% 5% 4 6% 19%	1330
December	1st to 10th	Day	3 13% 8% 15% 12% 6% 8% 5% 5% 5% 20%	1330
	11th to 20th	Day	1 21% 10% 18% 10% 5% 6% 5% 6% 6% 13%	1682
	21st to end	Day	1 17% 9% 12% 9% 4 5% 5% 5% 7% 25%	2442
January	1st to 10th	Night	1 10% 10% 28% 17% 6% 9% 4 3 4 8%	4726
	11th to 20th	Night	1 9% 8% 14% 11% 6% 7% 5% 7% 8% 25%	4538
	21st to end	Night	1 25% 13% 16% 9% 4 5% 4 4 4 12%	4862
February	1st to 10th	Night	2 13% 10% 19% 15% 5% 7% 6% 4 4 16%	2660
	11th to 20th	Night	2 12% 8% 18% 13% 5% 6% 6% 5% 6% 18%	2471
	21st to end	Night	1 9% 10% 18% 12% 8% 8% 5% 6% 6% 18%	1884
March	1st to 10th	Night	1 12% 10% 19% 12% 6% 7% 6% 5% 5% 17%	2280
	11th to 20th	Night	2 14% 12% 16% 11% 3 5% 5% 6% 7% 19%	2204
	21st to end	Night	2 14% 11% 19% 10% 5% 6% 6% 6% 5% 15%	2146
April	1st to 10th	Night	3 15% 11% 16% 10% 5% 7% 5% 6% 6% 17%	1820
	11th to 20th	Night	3 15% 9% 14% 10% 5% 6% 5% 7% 6% 21%	1628
	21st to end	Night	5% 17% 7% 9% 9% 6% 7% 6% 6% 6% 23%	1579
May	1st to 10th	Night	7% 17% 7% 10% 6% 4 6% 5% 6% 7% 26%	1440
	11th to 20th	Night	7% 9% 4 6% 6% 4 5% 6% 7% 8% 37%	1289
	21st to end	Night	13% 15% 3 7% 6% 4 6% 5% 7% 7% 27%	1358
June	1st to 10th	Night	17% 15% 5% 6% 5% 3 4 4 5% 7% 31%	1260
	11th to 20th	Night	14% 15% 5% 10% 8% 4 7% 5% 6% 6% 20%	1133
	21st to end	Night	8% 10% 3 6% 6% 5% 4 7% 7% 10% 34%	1080
July	1st to 10th	Night	9% 7% 2 5% 5% 3 6% 4 6% 9% 45%	1137
	11th to 20th	Night	10% 9% 3 6% 5% 3 6% 6% 6% 7% 39%	1260
	21st to end	Night	4 5% 2 4 5% 3 4 5% 5% 8% 54%	1538
August	1st to 10th	Night	7% 6% 4 4 5% 3 5% 5% 6% 8% 47%	1432
	11th to 20th	Night	10% 6% 2 5% 4 2 4 5% 8% 9% 46%	1464
	21st to end	Night	9% 11% 3 8% 6% 4 4 5% 7% 6% 39%	1799
September	1st to 10th	Night	8% 13% 4 7% 7% 4 4 4 4 6% 39%	1800
	11th to 20th	Night	13% 12% 4 7% 6% 3 4 4 4 7% 36%	1909
	21st to end	Night	9% 17% 5% 8% 5% 3 4 5% 6% 5% 33%	1980
October	1st to 10th	Night	9% 16% 5% 9% 6% 3 5% 5% 6% 7% 30%	2052
	11th to 20th	Night	7% 19% 6% 10% 7% 5% 6% 5% 5% 7% 24%	2340
	21st to end	Night	4 19% 9% 14% 8% 4 5% 5% 5% 7% 19%	2574
November	1st to 10th	Night	4 21% 10% 16% 10% 4 7% 5% 5% 5% 12%	2431
	11th to 20th	Night	2 16% 10% 20% 11% 6% 6% 4 5% 5% 16%	2850
	21st to end	Night	2 15% 9% 19% 11% 5% 6% 4 6% 7% 16%	2850
December	1st to 10th	Night	2 12% 10% 14% 15% 5% 6% 5% 4 5% 21%	2850
	11th to 20th	Night	1 15% 10% 18% 13% 9% 8% 6% 6% 4 11%	3510
	21st to end	Night	1 15% 7% 15% 11% 5% 6% 6% 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	70% 6% 8% 9% 4 2	1900
	11th to 20th	Day	66% 8% 8% 11% 6% 1	1976
	21st to end	Day	73% 8% 8% 7% 4 1	2451
April	1st to 10th	Day	73% 8% 10% 7% 2	2185
	11th to 20th	Day	69% 8% 9% 10% 3 1	2282
	21st to end	Day	68% 9% 9% 11% 2 1	2380
May	1st to 10th	Day	65% 9% 11% 12% 3	2520
	11th to 20th	Day	52% 10% 16% 16% 6%	2608
	21st to end	Day	59% 9% 13% 14% 5%	2918
June	1st to 10th	Day	60% 8% 14% 15% 3 1	2700
	11th to 20th	Day	61% 9% 13% 13% 3	2821
	21st to end	Day	49% 9% 18% 18% 5% 1	2880
July	1st to 10th	Day	46% 8% 15% 21% 9% 1	2744
	11th to 20th	Day	46% 8% 14% 23% 8%	2619
	21st to end	Day	40% 7% 12% 28% 14% 1	2622
August	1st to 10th	Day	45% 9% 15% 22% 9%	2490
	11th to 20th	Day	41% 9% 19% 21% 10%	2434
	21st to end	Day	52% 6% 13% 21% 8% 1	2556
September	1st to 10th	Day	50% 7% 16% 19% 7%	2160
	11th to 20th	Day	51% 7% 13% 20% 9%	2050
	21st to end	Day	58% 6% 13% 16% 7%	1980
October	1st to 10th	Day	59% 7% 9% 20% 6%	1908
	11th to 20th	Day	59% 9% 14% 15% 3	1620
	21st to end	Day	63% 9% 12% 9% 6% 1	1782
November	1st to 10th	Day	72% 5% 9% 9% 3 2	1627
	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	64% 7% 10% 11% 6% 1	2280
	11th to 20th	Night	62% 7% 11% 12% 7% 1	2204
	21st to end	Night	67% 7% 11% 10% 6%	2146
April	1st to 10th	Night	65% 8% 13% 11% 3	1820
	11th to 20th	Night	59% 8% 13% 13% 6% 1	1628
	21st to end	Night	57% 9% 12% 16% 5% 1	1579
May	1st to 10th	Night	55% 8% 14% 17% 6%	1440
	11th to 20th	Night	41% 9% 20% 22% 8%	1289
	21st to end	Night	53% 7% 14% 19% 6%	1358
June	1st to 10th	Night	53% 6% 14% 22% 4 1	1260
	11th to 20th	Night	60% 11% 12% 14% 4	1133
	21st to end	Night	40% 8% 20% 26% 5% 1	1080
July	1st to 10th	Night	36% 8% 16% 29% 11% 1	1104
	11th to 20th	Night	41% 7% 18% 25% 8% 1	1218
	21st to end	Night	27% 6% 16% 34% 15% 1	1453
August	1st to 10th	Night	31% 9% 21% 30% 8%	1424
	11th to 20th	Night	32% 7% 23% 29% 9%	1464
	21st to end	Night	42% 6% 16% 26% 9% 1	1799
September	1st to 10th	Night	44% 7% 16% 23% 9% 1	1800
	11th to 20th	Night	48% 6% 17% 19% 10% 1	1909
	21st to end	Night	49% 9% 15% 19% 8%	1980
October	1st to 10th	Night	53% 9% 13% 19% 6%	2052
	11th to 20th	Night	58% 7% 14% 16% 6%	2340
	21st to end	Night	62% 7% 12% 13% 6% 1	2574
November	1st to 10th	Night	71% 7% 7% 8% 5% 2	2431
	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% 23% 9% 3	506
April	1st to 10th	Day	13% 20% 35% 21% 9% 1	429
	11th to 20th	Day	15% 21% 33% 18% 10% 3	412
	21st to end	Day	17% 20% 27% 20% 13% 3	420
May	1st to 10th	Day	18% 17% 28% 22% 10% 4	423
	11th to 20th	Day	12% 9% 20% 29% 22% 8%	575
	21st to end	Day	18% 9% 18% 27% 21% 7%	679
June	1st to 10th	Day	20% 11% 24% 25% 16% 3	630
	11th to 20th	Day	20% 11% 25% 26% 15% 3	751
	21st to end	Day	13% 8% 20% 30% 22% 7%	810
July	1st to 10th	Day	13% 9% 20% 30% 23% 5%	739
	11th to 20th	Day	16% 9% 23% 30% 18% 5%	618
	21st to end	Day	11% 10% 25% 28% 20% 7%	522
August	1st to 10th	Day	12% 9% 28% 30% 18% 4	447
	11th to 20th	Day	12% 14% 31% 28% 11% 3	437
	21st to end	Day	20% 15% 29% 23% 11% 2	495
September	1st to 10th	Day	22% 21% 26% 21% 9% 1	450
	11th to 20th	Day	23% 15% 25% 27% 7% 2	450
	21st to end	Day	27% 20% 26% 17% 7% 2	450
October	1st to 10th	Day	24% 13% 27% 21% 12% 3	450
	11th to 20th	Day	20% 21% 24% 23% 10% 1	270
	21st to end	Day	16% 17% 34% 24% 7% 2	297
November	1st to 10th	Day	16% 18% 36% 18% 10% 2	261
	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% 28% 32% 18% 3	728
	11th to 20th	Night	7% 12% 30% 35% 15% 2	560
	21st to end	Night	12% 9% 24% 35% 16% 3	499
May	1st to 10th	Night	14% 6% 18% 37% 21% 4	360
	11th to 20th	Night	11% 4 16% 36% 29% 5%	354
	21st to end	Night	18% 8% 13% 28% 28% 5%	389
June	1st to 10th	Night	24% 5% 13% 33% 19% 5%	360
	11th to 20th	Night	21% 5% 19% 32% 20% 3	360
	21st to end	Night	11% 4 13% 33% 33% 7%	360
July	1st to 10th	Night	11% 3 11% 41% 31% 3	350
	11th to 20th	Night	16% 4 12% 39% 26% 3	348
	21st to end	Night	5% 3 13% 39% 35% 4	394
August	1st to 10th	Night	8% 3 8% 35% 41% 4	358
	11th to 20th	Night	12% 6% 12% 38% 28% 4	396
	21st to end	Night	13% 6% 17% 40% 22% 2	611
September	1st to 10th	Night	15% 6% 19% 33% 22% 5%	720
	11th to 20th	Night	17% 6% 15% 34% 22% 6%	720
	21st to end	Night	18% 11% 20% 31% 15% 4	720
October	1st to 10th	Night	16% 8% 20% 35% 17% 4	720
	11th to 20th	Night	15% 9% 26% 35% 12% 3	720
	21st to end	Night	13% 13% 31% 32% 11% 1	792
November	1st to 10th	Night	14% 11% 38% 26% 9% 2	749
	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 2024-03-31 04:08:55. Version ac07

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