Stony Plain
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Stony Plain clear sky chart from 2005-11-06 to 2024-02-05.

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	10% 9% 4 7% 7% 4 6% 5% 6% 8% 34%	78046
	Night	9% 10% 4 9% 7% 4 6% 5% 6% 8% 33%	80752
Transparency	Day	46% 8% 17% 21% 7% 1	77745
	Night	48% 8% 15% 19% 9% 1	80633
Seeing	Day	13% 7% 25% 31% 18% 6%	14741
	Night	13% 6% 28% 36% 16% 2	23518

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	4 13% 5% 9% 12% 4 6% 6% 6% 8% 26%	2219
	11th to 20th	Day	6% 10% 4 8% 7% 4 5% 7% 7% 8% 34%	2199
	21st to end	Day	8% 12% 4 8% 7% 4 5% 6% 6% 7% 34%	2648
February	1st to 10th	Day	10% 13% 5% 9% 8% 5% 6% 5% 7% 10% 22%	1472
	11th to 20th	Day	7% 12% 7% 11% 8% 5% 7% 6% 7% 6% 25%	1507
	21st to end	Day	4 12% 8% 9% 9% 6% 6% 7% 7% 9% 25%	1399
March	1st to 10th	Day	8% 14% 6% 10% 9% 5% 7% 5% 5% 6% 25%	1800
	11th to 20th	Day	9% 10% 5% 8% 6% 3 5% 6% 8% 9% 32%	1943
	21st to end	Day	10% 12% 7% 10% 7% 4 6% 6% 6% 8% 22%	2227
April	1st to 10th	Day	10% 11% 4 7% 8% 3 6% 7% 7% 7% 30%	2235
	11th to 20th	Day	12% 11% 4 8% 6% 4 6% 6% 7% 8% 29%	2310
	21st to end	Day	11% 10% 4 7% 6% 4 6% 5% 7% 8% 32%	2340
May	1st to 10th	Day	12% 9% 3 8% 8% 4 7% 6% 6% 8% 28%	2635
	11th to 20th	Day	9% 6% 3 6% 6% 4 6% 5% 6% 8% 41%	2654
	21st to end	Day	18% 8% 3 5% 6% 3 5% 5% 6% 8% 34%	2917
June	1st to 10th	Day	17% 8% 3 7% 6% 4 5% 5% 6% 8% 31%	2700
	11th to 20th	Day	19% 8% 4 7% 7% 5% 7% 6% 7% 8% 23%	2831
	21st to end	Day	11% 5% 2 5% 6% 4 6% 6% 7% 10% 38%	2880
July	1st to 10th	Day	11% 6% 3 7% 6% 4 5% 5% 7% 9% 38%	2818
	11th to 20th	Day	11% 6% 3 6% 6% 4 6% 6% 7% 10% 36%	2700
	21st to end	Day	9% 4 2 4 5% 3 6% 5% 6% 9% 46%	2938
August	1st to 10th	Day	10% 5% 2 6% 6% 3 6% 6% 8% 10% 38%	2555
	11th to 20th	Day	7% 5% 2 5% 6% 3 5% 5% 7% 10% 45%	2391
	21st to end	Day	11% 6% 2 5% 5% 4 5% 5% 7% 10% 41%	2574
September	1st to 10th	Day	12% 6% 3 6% 5% 3 5% 4 5% 8% 42%	2278
	11th to 20th	Day	14% 6% 2 6% 5% 3 4 5% 5% 9% 41%	1985
	21st to end	Day	9% 7% 2 7% 5% 4 5% 4 6% 9% 42%	1980
October	1st to 10th	Day	11% 10% 3 8% 8% 4 4 4 3 5% 39%	1887
	11th to 20th	Day	11% 10% 3 6% 7% 3 5% 4 6% 8% 37%	1629
	21st to end	Day	9% 13% 4 7% 7% 4 5% 5% 7% 7% 31%	1778
November	1st to 10th	Day	10% 15% 6% 10% 7% 4 6% 4 5% 8% 25%	1488
	11th to 20th	Day	8% 12% 5% 11% 7% 3 4 5% 5% 6% 32%	1345
	21st to end	Day	6% 10% 7% 12% 7% 5% 5% 5% 6% 8% 30%	1330
December	1st to 10th	Day	6% 12% 6% 11% 7% 5% 8% 6% 5% 8% 27%	1330
	11th to 20th	Day	7% 10% 5% 11% 9% 4 6% 7% 6% 7% 29%	1682
	21st to end	Day	4 7% 3 7% 7% 5% 6% 6% 6% 9% 40%	2442
January	1st to 10th	Night	5% 11% 6% 12% 10% 5% 6% 6% 6% 7% 26%	4726
	11th to 20th	Night	5% 8% 4 9% 10% 5% 7% 6% 7% 7% 33%	4699
	21st to end	Night	7% 14% 5% 10% 7% 3 5% 5% 5% 8% 32%	5026
February	1st to 10th	Night	6% 11% 6% 12% 9% 5% 6% 5% 5% 7% 27%	2582
	11th to 20th	Night	7% 13% 5% 10% 9% 4 7% 6% 6% 6% 27%	2339
	21st to end	Night	7% 10% 5% 7% 9% 6% 5% 6% 6% 8% 30%	1857
March	1st to 10th	Night	6% 11% 5% 10% 10% 4 5% 5% 7% 7% 28%	2160
	11th to 20th	Night	8% 10% 4 8% 8% 4 8% 6% 7% 8% 28%	2016
	21st to end	Night	9% 13% 6% 9% 7% 3 6% 6% 6% 9% 26%	2127
April	1st to 10th	Night	9% 10% 3 8% 8% 5% 7% 6% 7% 7% 29%	1724
	11th to 20th	Night	10% 11% 4 10% 9% 5% 5% 6% 6% 7% 28%	1601
	21st to end	Night	13% 9% 4 6% 5% 3 4 6% 6% 9% 34%	1620
May	1st to 10th	Night	12% 10% 4 8% 7% 5% 6% 6% 6% 7% 28%	1320
	11th to 20th	Night	10% 8% 4 7% 6% 4 5% 6% 6% 8% 36%	1239
	21st to end	Night	18% 9% 4 5% 6% 3 4 5% 7% 6% 32%	1358
June	1st to 10th	Night	16% 8% 4 7% 7% 3 6% 5% 5% 7% 32%	1260
	11th to 20th	Night	17% 8% 4 7% 8% 6% 7% 7% 5% 9% 20%	1125
	21st to end	Night	11% 5% 3 7% 6% 4 6% 7% 8% 9% 34%	1080
July	1st to 10th	Night	13% 5% 3 6% 5% 3 6% 5% 6% 9% 39%	1140
	11th to 20th	Night	10% 6% 2 6% 7% 4 7% 6% 8% 11% 33%	1260
	21st to end	Night	11% 5% 2 4 6% 3 5% 6% 7% 10% 42%	1379
August	1st to 10th	Night	11% 4 2 6% 7% 3 6% 6% 7% 8% 39%	1382
	11th to 20th	Night	10% 5% 2 5% 5% 3 5% 6% 6% 10% 42%	1509
	21st to end	Night	11% 6% 3 6% 6% 3 4 5% 7% 9% 39%	1782
September	1st to 10th	Night	12% 6% 3 6% 5% 3 4 6% 5% 8% 43%	1679
	11th to 20th	Night	12% 7% 2 5% 5% 3 5% 4 5% 8% 44%	1975
	21st to end	Night	10% 7% 2 6% 6% 3 4 5% 7% 8% 43%	1980
October	1st to 10th	Night	12% 8% 4 7% 6% 3 5% 4 6% 6% 39%	2072
	11th to 20th	Night	9% 9% 4 7% 5% 3 5% 5% 6% 8% 38%	2330
	21st to end	Night	8% 10% 4 8% 8% 4 6% 6% 6% 7% 34%	2574
November	1st to 10th	Night	14% 14% 5% 10% 7% 4 5% 5% 5% 7% 25%	2576
	11th to 20th	Night	8% 13% 5% 11% 7% 4 5% 5% 6% 7% 29%	2831
	21st to end	Night	7% 10% 6% 11% 8% 5% 6% 5% 5% 8% 29%	2850
December	1st to 10th	Night	9% 13% 5% 10% 8% 4 5% 5% 6% 8% 29%	2850
	11th to 20th	Night	7% 15% 6% 10% 8% 4 5% 5% 6% 7% 28%	3510
	21st to end	Night	3 8% 4 7% 7% 4 6% 5% 5% 9% 42%	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	53% 9% 12% 19% 6% 1	2219
	11th to 20th	Day	45% 6% 12% 14% 20% 2	2220
	21st to end	Day	47% 7% 21% 20% 5%	2648
February	1st to 10th	Day	55% 7% 16% 14% 7% 1	1472
	11th to 20th	Day	56% 8% 14% 15% 7%	1515
	21st to end	Day	52% 10% 14% 17% 7%	1399
March	1st to 10th	Day	58% 8% 15% 16% 4 1	1800
	11th to 20th	Day	46% 7% 16% 22% 10% 1	1944
	21st to end	Day	56% 8% 15% 15% 4	2227
April	1st to 10th	Day	48% 9% 17% 18% 7% 1	2235
	11th to 20th	Day	51% 7% 14% 21% 7%	2310
	21st to end	Day	47% 8% 15% 21% 7% 2	2340
May	1st to 10th	Day	51% 9% 14% 18% 8% 1	2635
	11th to 20th	Day	39% 7% 15% 28% 11% 1	2658
	21st to end	Day	47% 8% 14% 20% 10%	2918
June	1st to 10th	Day	50% 7% 16% 20% 7%	2700
	11th to 20th	Day	57% 10% 15% 14% 5%	2831
	21st to end	Day	38% 10% 23% 23% 5% 1	2880
July	1st to 10th	Day	41% 10% 19% 24% 5% 1	2742
	11th to 20th	Day	41% 12% 25% 21% 2	2619
	21st to end	Day	33% 10% 28% 25% 3	2775
August	1st to 10th	Day	37% 12% 26% 21% 3	2537
	11th to 20th	Day	34% 9% 26% 25% 6%	2391
	21st to end	Day	36% 9% 22% 25% 7%	2574
September	1st to 10th	Day	40% 8% 20% 23% 7% 2	2278
	11th to 20th	Day	39% 8% 18% 28% 7%	1985
	21st to end	Day	37% 9% 18% 26% 8% 2	1980
October	1st to 10th	Day	48% 6% 16% 21% 9%	1887
	11th to 20th	Day	44% 8% 17% 22% 9%	1629
	21st to end	Day	50% 9% 12% 22% 7%	1778
November	1st to 10th	Day	57% 8% 14% 15% 5% 1	1488
	11th to 20th	Day	51% 7% 16% 19% 7%	1345
	21st to end	Day	50% 9% 16% 17% 6% 1	1330
December	1st to 10th	Day	55% 8% 12% 17% 8% 1	1330
	11th to 20th	Day	52% 8% 16% 17% 7%	1684
	21st to end	Day	38% 7% 12% 26% 15% 2	2442
January	1st to 10th	Night	54% 8% 14% 15% 7% 2	4726
	11th to 20th	Night	48% 6% 13% 13% 17% 2	4740
	21st to end	Night	49% 8% 18% 17% 7%	5026
February	1st to 10th	Night	56% 6% 13% 16% 8% 1	2582
	11th to 20th	Night	55% 8% 14% 15% 9%	2341
	21st to end	Night	50% 8% 12% 19% 10% 1	1857
March	1st to 10th	Night	51% 8% 15% 19% 6% 1	2160
	11th to 20th	Night	50% 8% 11% 19% 11% 1	2016
	21st to end	Night	52% 10% 14% 17% 6% 1	2127
April	1st to 10th	Night	49% 9% 13% 18% 10% 1	1724
	11th to 20th	Night	53% 7% 12% 17% 9% 2	1601
	21st to end	Night	46% 7% 14% 20% 12% 1	1620
May	1st to 10th	Night	53% 6% 11% 19% 9% 1	1320
	11th to 20th	Night	45% 7% 12% 21% 14% 1	1239
	21st to end	Night	49% 7% 15% 16% 11% 2	1358
June	1st to 10th	Night	50% 9% 13% 20% 7%	1260
	11th to 20th	Night	58% 11% 15% 12% 3	1125
	21st to end	Night	41% 12% 22% 21% 4 1	1080
July	1st to 10th	Night	40% 11% 19% 22% 6% 1	1107
	11th to 20th	Night	42% 14% 23% 19% 3	1218
	21st to end	Night	36% 11% 22% 28% 4	1302
August	1st to 10th	Night	40% 11% 23% 24% 2	1375
	11th to 20th	Night	35% 10% 24% 24% 6% 1	1509
	21st to end	Night	38% 10% 18% 25% 9% 1	1782
September	1st to 10th	Night	38% 8% 20% 23% 9% 2	1679
	11th to 20th	Night	37% 7% 16% 28% 9% 2	1975
	21st to end	Night	37% 8% 15% 25% 13% 2	1980
October	1st to 10th	Night	44% 8% 14% 24% 10%	2072
	11th to 20th	Night	43% 8% 15% 25% 9% 1	2330
	21st to end	Night	47% 9% 14% 22% 7% 1	2574
November	1st to 10th	Night	58% 7% 11% 18% 6%	2576
	11th to 20th	Night	55% 8% 13% 18% 6% 1	2831
	21st to end	Night	52% 8% 16% 17% 5% 1	2850
December	1st to 10th	Night	53% 6% 13% 18% 9% 1	2850
	11th to 20th	Night	54% 8% 17% 15% 6%	3507
	21st to end	Night	39% 6% 16% 22% 14% 3	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	9% 7% 24% 38% 17% 4	180
	11th to 20th	Day	9% 7% 26% 36% 17% 6%	180
	21st to end	Day	14% 9% 27% 31% 13% 7%	198
February	1st to 10th	Day	17% 7% 30% 31% 12% 4	168
	11th to 20th	Day	13% 5% 32% 34% 12% 4	209
	21st to end	Day	7% 6% 32% 29% 18% 7%	265
March	1st to 10th	Day	13% 8% 27% 32% 17% 2	420
	11th to 20th	Day	11% 5% 27% 35% 16% 6%	420
	21st to end	Day	15% 6% 29% 27% 21% 3	462
April	1st to 10th	Day	9% 10% 31% 35% 11% 4	420
	11th to 20th	Day	15% 7% 23% 33% 16% 7%	412
	21st to end	Day	14% 10% 27% 29% 15% 4	420
May	1st to 10th	Day	14% 10% 25% 32% 16% 3	547
	11th to 20th	Day	12% 5% 24% 35% 19% 6%	625
	21st to end	Day	18% 5% 20% 32% 18% 8%	679
June	1st to 10th	Day	19% 7% 24% 33% 13% 4	630
	11th to 20th	Day	20% 7% 22% 27% 20% 5%	761
	21st to end	Day	12% 4 19% 31% 26% 8%	810
July	1st to 10th	Day	12% 5% 19% 34% 22% 8%	737
	11th to 20th	Day	11% 3 22% 33% 24% 6%	618
	21st to end	Day	9% 4 17% 35% 25% 9%	684
August	1st to 10th	Day	10% 6% 17% 32% 22% 13%	495
	11th to 20th	Day	7% 4 28% 31% 24% 5%	437
	21st to end	Day	14% 6% 17% 31% 22% 9%	495
September	1st to 10th	Day	16% 8% 30% 22% 19% 5%	450
	11th to 20th	Day	18% 6% 24% 28% 18% 6%	450
	21st to end	Day	11% 12% 30% 27% 16% 5%	450
October	1st to 10th	Day	15% 8% 23% 32% 17% 4	357
	11th to 20th	Day	13% 10% 30% 29% 14% 4	270
	21st to end	Day	14% 12% 37% 25% 10% 2	297
November	1st to 10th	Day	17% 6% 33% 29% 12% 3	270
	11th to 20th	Day	13% 6% 39% 27% 13% 2	187
	21st to end	Day	7% 7% 36% 35% 10% 6%	180
December	1st to 10th	Day	8% 8% 29% 35% 14% 6%	180
	11th to 20th	Day	11% 8% 32% 34% 13% 3	180
	21st to end	Day	8% 4 21% 39% 23% 5%	198
January	1st to 10th	Night	11% 7% 32% 34% 15% 2	950
	11th to 20th	Night	12% 7% 31% 36% 13% 1	950
	21st to end	Night	13% 11% 32% 32% 11% 1	935
February	1st to 10th	Night	12% 8% 25% 35% 17% 3	738
	11th to 20th	Night	12% 5% 33% 33% 15% 1	704
	21st to end	Night	9% 4 27% 37% 18% 5%	592
March	1st to 10th	Night	11% 4 28% 37% 18% 2	720
	11th to 20th	Night	12% 3 29% 37% 17% 2	720
	21st to end	Night	14% 4 25% 37% 16% 3	792
April	1st to 10th	Night	11% 6% 26% 37% 17% 2	644
	11th to 20th	Night	14% 5% 31% 33% 16% 1	533
	21st to end	Night	16% 6% 28% 36% 14% 1	540
May	1st to 10th	Night	15% 6% 24% 37% 17% 1	365
	11th to 20th	Night	11% 4 25% 40% 18% 1	354
	21st to end	Night	22% 6% 20% 34% 16% 2	389
June	1st to 10th	Night	17% 8% 23% 37% 13% 2	360
	11th to 20th	Night	19% 6% 20% 31% 21% 2	360
	21st to end	Night	12% 4 17% 38% 26% 3	360
July	1st to 10th	Night	14% 1 17% 43% 24% 1	350
	11th to 20th	Night	12% 4 20% 40% 22% 2	348
	21st to end	Night	12% 4 16% 39% 27% 2	394
August	1st to 10th	Night	13% 4 15% 33% 30% 5%	358
	11th to 20th	Night	11% 5% 17% 37% 27% 2	441
	21st to end	Night	13% 3 20% 39% 24% 1	594
September	1st to 10th	Night	15% 3 20% 41% 20% 2	599
	11th to 20th	Night	14% 4 21% 40% 20% 2	720
	21st to end	Night	13% 4 29% 36% 16% 2	720
October	1st to 10th	Night	15% 4 26% 39% 15%	720
	11th to 20th	Night	13% 5% 32% 33% 15% 2	720
	21st to end	Night	13% 8% 33% 32% 13% 1	792
November	1st to 10th	Night	20% 6% 29% 33% 11% 1	911
	11th to 20th	Night	13% 9% 35% 30% 11% 3	950
	21st to end	Night	10% 6% 37% 36% 10% 1	950
December	1st to 10th	Night	13% 8% 31% 31% 14% 3	950
	11th to 20th	Night	11% 7% 31% 35% 14% 1	950
	21st to end	Night	10% 4 29% 36% 17% 3	1045

Page generated at 2024-02-02 03:20:31. Version ac07

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