Spruce Woods Provincial Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Spruce Woods Provincial Park clear sky chart from 2005-11-06 to 2025-07-21.

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	11% 9% 3 9% 5% 5% 5% 4 6% 8% 35%	123950
	Night	9% 10% 4 10% 6% 5% 5% 4 6% 7% 35%	123931
Transparency	Day	46% 7% 15% 24% 9%	123702
	Night	47% 6% 14% 23% 9% 1	123825
Seeing	Day	15% 9% 31% 28% 14% 3	17226
	Night	14% 7% 32% 34% 12% 1	27162

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 15% 6% 15% 9% 7% 6% 6% 8% 9% 16%	3179
	11th to 20th	Day	4 9% 4 12% 9% 10% 12% 8% 8% 9% 16%	3415
	21st to end	Day	6% 12% 5% 13% 6% 6% 7% 4 6% 6% 28%	4004
February	1st to 10th	Day	10% 12% 5% 12% 8% 7% 7% 5% 9% 6% 19%	1618
	11th to 20th	Day	6% 9% 5% 10% 10% 7% 6% 6% 7% 9% 26%	1770
	21st to end	Day	6% 12% 4 12% 9% 7% 6% 5% 6% 6% 27%	1650
March	1st to 10th	Day	8% 11% 4 11% 7% 6% 6% 5% 7% 10% 25%	4500
	11th to 20th	Day	8% 15% 6% 12% 7% 6% 5% 4 6% 7% 24%	4923
	21st to end	Day	10% 12% 6% 15% 8% 7% 5% 3 5% 6% 24%	5550
April	1st to 10th	Day	10% 11% 4 8% 5% 4 5% 4 6% 8% 36%	2426
	11th to 20th	Day	13% 11% 4 10% 7% 4 5% 4 5% 6% 30%	2572
	21st to end	Day	15% 9% 3 8% 5% 5% 5% 4 6% 6% 34%	2600
May	1st to 10th	Day	15% 7% 2 5% 3 3 4 3 6% 7% 44%	6019
	11th to 20th	Day	21% 10% 3 8% 5% 5% 4 4 5% 7% 28%	6681
	21st to end	Day	14% 6% 2 5% 3 4 4 3 5% 7% 47%	7428
June	1st to 10th	Day	14% 7% 2 6% 5% 5% 5% 4 7% 8% 37%	3000
	11th to 20th	Day	14% 6% 3 6% 6% 5% 6% 4 7% 8% 35%	3000
	21st to end	Day	12% 6% 2 6% 5% 4 5% 5% 7% 10% 37%	3000
July	1st to 10th	Day	9% 4 1 5% 4 5% 6% 5% 9% 10% 42%	4900
	11th to 20th	Day	8% 4 2 5% 4 4 5% 4 7% 9% 47%	4900
	21st to end	Day	5% 3 2 5% 4 4 5% 4 8% 10% 50%	4876
August	1st to 10th	Day	9% 5% 3 6% 4 4 5% 4 7% 9% 45%	4412
	11th to 20th	Day	10% 5% 2 4 3 4 4 4 6% 9% 47%	4041
	21st to end	Day	10% 6% 2 6% 4 3 4 3 5% 9% 48%	4532
September	1st to 10th	Day	11% 5% 2 6% 3 4 4 3 5% 7% 51%	2321
	11th to 20th	Day	14% 6% 2 7% 5% 3 3 3 5% 7% 44%	2090
	21st to end	Day	15% 6% 2 7% 3 3 3 3 6% 7% 45%	2090
October	1st to 10th	Day	13% 8% 2 6% 4 3 3 2 5% 6% 48%	3335
	11th to 20th	Day	9% 8% 2 7% 5% 4 4 3 5% 8% 44%	2925
	21st to end	Day	14% 12% 4 8% 3 4 4 4 5% 7% 35%	3091
November	1st to 10th	Day	18% 14% 5% 10% 5% 4 4 3 4 5% 30%	1700
	11th to 20th	Day	8% 16% 6% 12% 8% 4 3 3 5% 6% 29%	1575
	21st to end	Day	10% 14% 4 11% 9% 5% 5% 4 4 5% 28%	1400
December	1st to 10th	Day	8% 13% 6% 18% 11% 9% 7% 4 5% 5% 14%	2290
	11th to 20th	Day	9% 12% 6% 12% 7% 7% 6% 5% 7% 8% 20%	2639
	21st to end	Day	6% 9% 5% 16% 7% 6% 5% 4 5% 6% 32%	3498
January	1st to 10th	Night	4 12% 6% 18% 10% 8% 7% 4 6% 7% 18%	6787
	11th to 20th	Night	5% 11% 5% 13% 8% 8% 9% 8% 8% 8% 17%	6486
	21st to end	Night	7% 15% 7% 14% 7% 5% 5% 4 5% 7% 24%	6974
February	1st to 10th	Night	8% 12% 5% 11% 8% 6% 7% 6% 5% 6% 26%	2781
	11th to 20th	Night	6% 9% 4 9% 6% 6% 7% 5% 7% 7% 34%	2533
	21st to end	Night	7% 11% 4 9% 7% 5% 5% 4 6% 8% 33%	1980
March	1st to 10th	Night	8% 10% 4 10% 7% 5% 6% 4 7% 9% 29%	5374
	11th to 20th	Night	7% 13% 5% 11% 6% 5% 4 3 5% 7% 33%	5036
	21st to end	Night	9% 14% 5% 13% 7% 5% 5% 3 5% 6% 29%	5382
April	1st to 10th	Night	7% 8% 4 8% 6% 5% 4 5% 6% 8% 42%	1973
	11th to 20th	Night	13% 14% 3 8% 6% 4 5% 3 6% 6% 33%	1779
	21st to end	Night	13% 10% 3 7% 5% 5% 5% 5% 5% 7% 37%	1800
May	1st to 10th	Night	16% 7% 3 6% 4 4 4 3 4 6% 42%	3958
	11th to 20th	Night	17% 9% 2 6% 4 4 5% 4 6% 9% 33%	3235
	21st to end	Night	14% 6% 2 5% 4 3 3 3 4 5% 51%	3470
June	1st to 10th	Night	11% 7% 2 5% 3 4 5% 5% 6% 9% 43%	1400
	11th to 20th	Night	11% 6% 2 6% 6% 5% 4 4 6% 8% 43%	1400
	21st to end	Night	10% 5% 1 5% 4 5% 5% 4 7% 10% 43%	1400
July	1st to 10th	Night	9% 3 1 4 4 4 5% 5% 7% 10% 48%	2290
	11th to 20th	Night	7% 3 2 4 3 4 4 4 7% 8% 56%	2290
	21st to end	Night	4 4 1 4 4 5% 5% 5% 7% 8% 54%	2685
August	1st to 10th	Night	6% 4 2 6% 4 4 5% 4 6% 8% 51%	2528
	11th to 20th	Night	6% 4 2 5% 4 4 5% 4 6% 11% 50%	2798
	21st to end	Night	11% 5% 2 4 3 3 3 3 5% 7% 53%	3135
September	1st to 10th	Night	8% 5% 2 5% 4 3 4 4 6% 8% 53%	1856
	11th to 20th	Night	13% 5% 2 4 4 4 4 2 6% 8% 48%	2090
	21st to end	Night	15% 7% 2 6% 4 3 4 3 5% 7% 44%	2090
October	1st to 10th	Night	12% 8% 2 5% 4 4 3 3 4 7% 47%	3592
	11th to 20th	Night	10% 7% 2 6% 4 4 4 4 6% 8% 44%	3998
	21st to end	Night	7% 9% 3 7% 5% 4 5% 4 6% 6% 43%	4467
November	1st to 10th	Night	12% 12% 4 8% 6% 4 5% 4 6% 7% 32%	2596
	11th to 20th	Night	10% 16% 6% 12% 6% 4 4 3 5% 6% 28%	2820
	21st to end	Night	10% 13% 5% 11% 7% 5% 5% 3 4 6% 31%	3000
December	1st to 10th	Night	8% 14% 5% 17% 9% 8% 5% 4 6% 5% 18%	4900
	11th to 20th	Night	9% 14% 5% 12% 7% 7% 6% 4 5% 7% 24%	5568
	21st to end	Night	6% 9% 4 14% 7% 7% 6% 4 5% 6% 31%	7480

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	63% 6% 11% 16% 3	3179
	11th to 20th	Day	60% 7% 10% 17% 6%	3438
	21st to end	Day	55% 7% 15% 20% 4	4004
February	1st to 10th	Day	60% 7% 11% 16% 7%	1618
	11th to 20th	Day	51% 8% 11% 19% 10%	1779
	21st to end	Day	55% 7% 13% 18% 7%	1650
March	1st to 10th	Day	52% 7% 18% 15% 7%	4500
	11th to 20th	Day	57% 7% 14% 18% 5%	4925
	21st to end	Day	59% 6% 9% 19% 6%	5550
April	1st to 10th	Day	45% 6% 14% 25% 9% 1	2426
	11th to 20th	Day	54% 5% 12% 18% 10% 1	2572
	21st to end	Day	48% 7% 15% 21% 8% 1	2600
May	1st to 10th	Day	39% 5% 14% 26% 16% 1	6019
	11th to 20th	Day	54% 6% 9% 23% 7% 1	6685
	21st to end	Day	36% 7% 8% 24% 23% 1	7428
June	1st to 10th	Day	42% 8% 16% 22% 10% 1	3000
	11th to 20th	Day	45% 8% 16% 21% 10% 1	3000
	21st to end	Day	40% 10% 19% 24% 6% 1	3000
July	1st to 10th	Day	33% 10% 27% 25% 5%	4826
	11th to 20th	Day	31% 7% 20% 35% 7%	4819
	21st to end	Day	27% 7% 24% 32% 9%	4722
August	1st to 10th	Day	35% 7% 18% 29% 10%	4396
	11th to 20th	Day	32% 7% 20% 34% 7%	4080
	21st to end	Day	34% 5% 21% 31% 8%	4531
September	1st to 10th	Day	33% 5% 16% 33% 11% 2	2321
	11th to 20th	Day	40% 7% 16% 26% 9% 1	2090
	21st to end	Day	40% 6% 15% 30% 10%	2090
October	1st to 10th	Day	38% 4 11% 38% 9%	3335
	11th to 20th	Day	39% 5% 12% 33% 11%	2925
	21st to end	Day	49% 5% 11% 26% 8%	3091
November	1st to 10th	Day	57% 4 13% 18% 7% 1	1700
	11th to 20th	Day	56% 5% 15% 17% 6%	1575
	21st to end	Day	56% 9% 14% 16% 5%	1400
December	1st to 10th	Day	72% 6% 11% 9% 2	2290
	11th to 20th	Day	59% 7% 15% 14% 5%	2640
	21st to end	Day	53% 6% 9% 22% 10%	3498
January	1st to 10th	Night	62% 7% 9% 18% 4	6787
	11th to 20th	Night	60% 7% 11% 17% 5%	6524
	21st to end	Night	60% 7% 11% 18% 4	6974
February	1st to 10th	Night	56% 6% 12% 16% 9%	2781
	11th to 20th	Night	46% 8% 13% 21% 12%	2534
	21st to end	Night	47% 6% 14% 23% 10%	1980
March	1st to 10th	Night	49% 7% 16% 19% 8% 1	5374
	11th to 20th	Night	49% 5% 14% 21% 11%	5036
	21st to end	Night	55% 5% 10% 24% 6%	5382
April	1st to 10th	Night	38% 6% 12% 25% 16% 2	1973
	11th to 20th	Night	52% 6% 9% 20% 12% 1	1779
	21st to end	Night	46% 6% 14% 20% 13% 2	1800
May	1st to 10th	Night	43% 5% 9% 23% 18%	3958
	11th to 20th	Night	47% 7% 11% 24% 8% 3	3235
	21st to end	Night	35% 5% 10% 21% 27% 3	3470
June	1st to 10th	Night	36% 7% 19% 25% 11% 2	1400
	11th to 20th	Night	38% 8% 15% 26% 11% 2	1400
	21st to end	Night	34% 9% 22% 27% 7% 1	1400
July	1st to 10th	Night	29% 9% 25% 28% 8% 1	2255
	11th to 20th	Night	24% 7% 18% 41% 10% 1	2248
	21st to end	Night	25% 6% 24% 33% 11% 1	2600
August	1st to 10th	Night	30% 6% 16% 32% 14% 2	2520
	11th to 20th	Night	28% 7% 21% 33% 10% 1	2825
	21st to end	Night	32% 6% 18% 34% 10% 1	3135
September	1st to 10th	Night	29% 6% 13% 34% 15% 2	1856
	11th to 20th	Night	35% 6% 18% 27% 13% 1	2090
	21st to end	Night	40% 6% 11% 31% 11% 1	2090
October	1st to 10th	Night	37% 4 13% 30% 15% 2	3592
	11th to 20th	Night	37% 4 12% 32% 13% 1	3998
	21st to end	Night	41% 5% 13% 34% 7%	4467
November	1st to 10th	Night	50% 7% 15% 19% 7% 2	2596
	11th to 20th	Night	57% 7% 14% 15% 6% 1	2820
	21st to end	Night	55% 7% 15% 18% 6%	3000
December	1st to 10th	Night	67% 6% 12% 11% 4	4900
	11th to 20th	Night	60% 6% 14% 15% 4	5566
	21st to end	Night	52% 6% 13% 18% 9% 1	7480

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	10% 11% 32% 31% 13% 3	300
	11th to 20th	Day	9% 12% 35% 31% 11% 2	300
	21st to end	Day	14% 10% 33% 29% 11% 2	330
February	1st to 10th	Day	17% 10% 40% 24% 7% 1	300
	11th to 20th	Day	6% 11% 39% 31% 11% 1	300
	21st to end	Day	6% 10% 41% 30% 12% 1	249
March	1st to 10th	Day	16% 12% 30% 29% 10% 3	300
	11th to 20th	Day	14% 12% 31% 28% 13% 2	300
	21st to end	Day	16% 8% 38% 23% 13% 2	365
April	1st to 10th	Day	16% 14% 33% 27% 7% 2	526
	11th to 20th	Day	18% 12% 35% 22% 11% 1	690
	21st to end	Day	18% 12% 31% 27% 12% 1	700
May	1st to 10th	Day	17% 10% 30% 27% 14% 2	703
	11th to 20th	Day	19% 10% 33% 23% 13% 3	725
	21st to end	Day	19% 11% 22% 27% 17% 4	789
June	1st to 10th	Day	16% 12% 28% 25% 14% 5%	730
	11th to 20th	Day	17% 10% 33% 25% 12% 3	730
	21st to end	Day	13% 8% 28% 30% 17% 4	730
July	1st to 10th	Day	9% 4 28% 29% 21% 8%	721
	11th to 20th	Day	11% 7% 31% 28% 19% 5%	718
	21st to end	Day	6% 5% 26% 34% 21% 7%	740
August	1st to 10th	Day	9% 6% 25% 32% 22% 7%	676
	11th to 20th	Day	12% 6% 22% 28% 23% 9%	665
	21st to end	Day	13% 8% 25% 32% 18% 4	748
September	1st to 10th	Day	12% 8% 34% 29% 14% 4	531
	11th to 20th	Day	18% 7% 30% 32% 11% 3	300
	21st to end	Day	21% 10% 31% 26% 11% 1	300
October	1st to 10th	Day	26% 13% 25% 23% 11% 3	300
	11th to 20th	Day	16% 11% 34% 28% 8% 2	300
	21st to end	Day	23% 8% 37% 22% 7% 2	330
November	1st to 10th	Day	28% 9% 31% 22% 9% 1	300
	11th to 20th	Day	17% 13% 33% 28% 9%	300
	21st to end	Day	16% 11% 39% 28% 5% 1	300
December	1st to 10th	Day	17% 9% 35% 27% 10% 2	300
	11th to 20th	Day	15% 12% 41% 27% 4 1	300
	21st to end	Day	12% 5% 37% 32% 12% 3	330
January	1st to 10th	Night	11% 9% 37% 31% 11% 1	1000
	11th to 20th	Night	14% 7% 39% 31% 8% 1	1000
	21st to end	Night	15% 8% 36% 33% 8% 1	1100
February	1st to 10th	Night	14% 8% 36% 31% 11% 1	1000
	11th to 20th	Night	10% 7% 33% 37% 11% 2	979
	21st to end	Night	12% 5% 34% 36% 11% 2	660
March	1st to 10th	Night	15% 7% 31% 33% 12% 2	800
	11th to 20th	Night	11% 8% 36% 32% 12% 2	630
	21st to end	Night	16% 7% 30% 33% 13% 2	660
April	1st to 10th	Night	10% 7% 34% 38% 10% 1	600
	11th to 20th	Night	19% 7% 31% 33% 10% 1	593
	21st to end	Night	17% 6% 32% 34% 10% 1	600
May	1st to 10th	Night	17% 6% 28% 37% 11% 1	600
	11th to 20th	Night	17% 8% 26% 35% 12%	591
	21st to end	Night	20% 7% 26% 33% 13%	650
June	1st to 10th	Night	14% 7% 34% 31% 14% 2	600
	11th to 20th	Night	12% 6% 32% 37% 13% 1	600
	21st to end	Night	12% 6% 25% 39% 17% 1	600
July	1st to 10th	Night	7% 3 25% 41% 22% 2	585
	11th to 20th	Night	8% 5% 27% 42% 18% 1	582
	21st to end	Night	7% 3 23% 46% 19% 3	624
August	1st to 10th	Night	8% 3 24% 44% 21% 1	567
	11th to 20th	Night	8% 4 23% 38% 25% 3	564
	21st to end	Night	12% 6% 24% 41% 16% 2	627
September	1st to 10th	Night	10% 4 29% 37% 18% 2	570
	11th to 20th	Night	14% 8% 28% 41% 9%	570
	21st to end	Night	17% 8% 29% 33% 11% 1	570
October	1st to 10th	Night	18% 8% 34% 30% 10%	630
	11th to 20th	Night	19% 8% 30% 32% 10%	890
	21st to end	Night	16% 11% 35% 28% 8% 1	1045
November	1st to 10th	Night	17% 8% 38% 28% 8% 1	975
	11th to 20th	Night	17% 9% 36% 28% 8% 2	1000
	21st to end	Night	16% 12% 38% 27% 7% 1	1000
December	1st to 10th	Night	12% 9% 35% 33% 10% 2	1000
	11th to 20th	Night	17% 9% 35% 28% 8% 2	1000
	21st to end	Night	17% 5% 33% 32% 11% 2	1100

Page generated at 2025-07-18 00:10:03. Version ac07

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