Sparwood
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Sparwood clear sky chart from 2005-11-06 to 2026-02-16.

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% 13% 5% 10% 6% 5% 5% 4 6% 7% 33%	134653
	Night	5% 15% 6% 13% 6% 5% 5% 4 5% 7% 29%	134913
Transparency	Day	48% 8% 14% 19% 9% 2	134367
	Night	52% 9% 15% 16% 7% 1	134778
Seeing	Day	20% 20% 30% 19% 8% 2	16783
	Night	15% 14% 31% 28% 11% 1	26074

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 20% 12% 29% 8% 6% 4 3 3 4 8%	4125
	11th to 20th	Day	3 13% 5% 13% 9% 7% 6% 4 6% 8% 27%	4573
	21st to end	Day	2 20% 7% 9% 6% 5% 5% 5% 6% 6% 27%	5186
February	1st to 10th	Day	4 16% 9% 16% 9% 6% 6% 4 5% 6% 18%	1680
	11th to 20th	Day	3 17% 8% 17% 8% 6% 5% 4 6% 6% 19%	1811
	21st to end	Day	3 19% 7% 15% 9% 8% 6% 4 6% 5% 18%	1650
March	1st to 10th	Day	3 17% 6% 15% 5% 5% 4 4 6% 7% 27%	4518
	11th to 20th	Day	3 24% 7% 12% 6% 5% 4 4 4 5% 26%	4884
	21st to end	Day	6% 31% 6% 14% 6% 5% 4 3 5% 5% 16%	5651
April	1st to 10th	Day	6% 21% 6% 14% 6% 6% 5% 4 5% 6% 21%	2404
	11th to 20th	Day	7% 21% 6% 12% 6% 5% 5% 4 6% 6% 23%	2570
	21st to end	Day	10% 17% 5% 10% 7% 6% 5% 4 5% 6% 25%	2600
May	1st to 10th	Day	11% 15% 4 8% 4 4 4 3 5% 7% 35%	6073
	11th to 20th	Day	10% 14% 4 11% 8% 7% 7% 6% 7% 7% 18%	6586
	21st to end	Day	11% 12% 3 8% 6% 5% 6% 4 6% 7% 31%	7405
June	1st to 10th	Day	15% 12% 4 9% 7% 5% 5% 5% 6% 7% 26%	3000
	11th to 20th	Day	17% 11% 3 9% 6% 6% 6% 5% 7% 6% 23%	3000
	21st to end	Day	9% 7% 3 7% 5% 5% 6% 5% 8% 7% 38%	3000
July	1st to 10th	Day	5% 4 2 4 4 5% 4 4 6% 8% 56%	6780
	11th to 20th	Day	5% 3 1 4 4 4 4 4 6% 9% 57%	6780
	21st to end	Day	5% 3 1 3 2 3 4 4 7% 9% 58%	6885
August	1st to 10th	Day	5% 5% 2 5% 4 5% 6% 4 7% 9% 47%	4541
	11th to 20th	Day	6% 4 2 5% 4 4 5% 4 7% 8% 52%	4197
	21st to end	Day	6% 5% 2 5% 4 5% 5% 4 6% 8% 51%	4664
September	1st to 10th	Day	8% 7% 3 5% 3 5% 4 3 5% 7% 48%	2425
	11th to 20th	Day	9% 7% 2 7% 5% 5% 4 5% 6% 7% 42%	2206
	21st to end	Day	9% 11% 3 6% 4 4 5% 4 6% 7% 42%	2200
October	1st to 10th	Day	6% 9% 2 7% 3 4 4 4 6% 8% 46%	3534
	11th to 20th	Day	10% 11% 2 7% 5% 3 4 4 6% 9% 39%	2969
	21st to end	Day	9% 21% 6% 10% 6% 4 4 4 5% 6% 25%	3200
November	1st to 10th	Day	10% 22% 7% 15% 7% 5% 4 3 4 5% 19%	1822
	11th to 20th	Day	6% 19% 7% 14% 7% 6% 6% 4 5% 5% 20%	1617
	21st to end	Day	5% 17% 8% 17% 10% 4 4 3 5% 7% 20%	1470
December	1st to 10th	Day	3 14% 6% 18% 13% 8% 5% 4 5% 7% 18%	2360
	11th to 20th	Day	2 19% 10% 25% 10% 5% 4 3 4 4 13%	2712
	21st to end	Day	2 23% 10% 19% 8% 7% 5% 3 4 5% 13%	3575
January	1st to 10th	Night	2 20% 16% 29% 8% 5% 4 2 3 4 8%	8768
	11th to 20th	Night	3 13% 4 16% 9% 7% 7% 5% 6% 7% 25%	8383
	21st to end	Night	3 21% 7% 12% 7% 6% 5% 4 6% 8% 20%	8994
February	1st to 10th	Night	3 19% 8% 19% 10% 7% 4 3 6% 6% 14%	2940
	11th to 20th	Night	3 18% 9% 16% 7% 5% 5% 3 5% 7% 21%	2580
	21st to end	Night	2 18% 6% 17% 10% 6% 6% 4 5% 6% 21%	1980
March	1st to 10th	Night	2 17% 6% 15% 6% 4 4 4 7% 9% 26%	5376
	11th to 20th	Night	4 20% 6% 11% 6% 5% 5% 4 6% 7% 26%	5115
	21st to end	Night	6% 29% 8% 13% 6% 5% 4 3 5% 6% 16%	5322
April	1st to 10th	Night	6% 16% 5% 10% 6% 5% 4 4 6% 8% 29%	1995
	11th to 20th	Night	5% 16% 5% 10% 6% 5% 5% 4 5% 8% 31%	1781
	21st to end	Night	7% 15% 4 10% 5% 5% 4 4 6% 6% 33%	1800
May	1st to 10th	Night	8% 16% 3 8% 4 3 3 3 4 7% 40%	3881
	11th to 20th	Night	10% 13% 4 10% 6% 6% 6% 5% 8% 9% 24%	3304
	21st to end	Night	11% 12% 3 7% 4 4 5% 3 5% 6% 40%	3470
June	1st to 10th	Night	13% 10% 3 6% 4 5% 5% 6% 6% 8% 34%	1400
	11th to 20th	Night	15% 9% 2 7% 5% 6% 5% 5% 7% 7% 31%	1400
	21st to end	Night	7% 5% 2 6% 5% 5% 5% 5% 8% 8% 46%	1400
July	1st to 10th	Night	5% 3 1 4 4 3 4 4 6% 7% 60%	3180
	11th to 20th	Night	5% 2 1 3 3 4 4 4 5% 8% 60%	3180
	21st to end	Night	6% 4 1 4 3 3 3 3 5% 6% 61%	3955
August	1st to 10th	Night	6% 6% 2 5% 4 4 5% 3 5% 7% 54%	2609
	11th to 20th	Night	5% 3 2 4 4 3 5% 4 6% 10% 54%	2861
	21st to end	Night	7% 4 2 4 2 3 3 4 6% 9% 56%	3245
September	1st to 10th	Night	6% 4 2 5% 2 3 4 3 5% 7% 58%	1973
	11th to 20th	Night	9% 7% 3 6% 5% 3 3 3 6% 8% 48%	2193
	21st to end	Night	9% 10% 2 5% 4 3 4 3 6% 8% 46%	2200
October	1st to 10th	Night	6% 9% 2 6% 3 3 3 4 6% 8% 50%	3664
	11th to 20th	Night	8% 11% 3 7% 3 4 3 3 6% 7% 45%	4175
	21st to end	Night	6% 17% 5% 11% 5% 5% 4 4 7% 8% 29%	4600
November	1st to 10th	Night	10% 22% 6% 13% 5% 5% 4 4 6% 6% 20%	2676
	11th to 20th	Night	5% 23% 8% 15% 8% 5% 4 4 5% 6% 18%	3000
	21st to end	Night	4 19% 8% 19% 9% 6% 4 3 4 7% 17%	3150
December	1st to 10th	Night	3 13% 6% 19% 10% 8% 7% 4 7% 7% 16%	5040
	11th to 20th	Night	2 21% 11% 22% 12% 8% 5% 3 4 4 9%	5700
	21st to end	Night	3 26% 11% 19% 8% 6% 5% 4 4 4 10%	7623

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	76% 10% 8% 5% 1	4125
	11th to 20th	Day	52% 9% 15% 14% 7% 2	4597
	21st to end	Day	53% 9% 17% 14% 6%	5187
February	1st to 10th	Day	66% 7% 13% 8% 5% 1	1680
	11th to 20th	Day	63% 9% 12% 10% 6%	1820
	21st to end	Day	64% 8% 12% 10% 5% 1	1650
March	1st to 10th	Day	53% 7% 16% 12% 12%	4518
	11th to 20th	Day	56% 10% 18% 14% 3	4885
	21st to end	Day	69% 8% 10% 8% 5%	5651
April	1st to 10th	Day	63% 7% 16% 12% 2	2404
	11th to 20th	Day	59% 8% 15% 14% 3	2570
	21st to end	Day	58% 8% 14% 17% 3 1	2600
May	1st to 10th	Day	49% 5% 10% 24% 12%	6073
	11th to 20th	Day	56% 12% 14% 15% 3	6590
	21st to end	Day	48% 9% 17% 20% 6%	7406
June	1st to 10th	Day	56% 7% 14% 17% 6% 1	3000
	11th to 20th	Day	58% 8% 13% 13% 7% 1	3000
	21st to end	Day	40% 9% 16% 22% 11% 1	3000
July	1st to 10th	Day	24% 8% 12% 25% 25% 6%	6706
	11th to 20th	Day	23% 7% 13% 28% 24% 5%	6699
	21st to end	Day	21% 6% 14% 31% 19% 9%	6691
August	1st to 10th	Day	30% 9% 14% 26% 19% 3	4524
	11th to 20th	Day	27% 8% 20% 32% 12% 1	4236
	21st to end	Day	29% 8% 19% 31% 13% 1	4663
September	1st to 10th	Day	33% 6% 16% 27% 15% 3	2425
	11th to 20th	Day	39% 7% 15% 28% 11% 1	2206
	21st to end	Day	40% 8% 20% 22% 10% 1	2200
October	1st to 10th	Day	33% 8% 22% 31% 6%	3534
	11th to 20th	Day	42% 8% 18% 23% 9%	2969
	21st to end	Day	54% 11% 15% 14% 6%	3200
November	1st to 10th	Day	66% 9% 11% 10% 3	1822
	11th to 20th	Day	62% 11% 15% 9% 4	1617
	21st to end	Day	62% 9% 13% 10% 5%	1470
December	1st to 10th	Day	63% 11% 13% 10% 3 1	2360
	11th to 20th	Day	72% 9% 11% 6% 2	2714
	21st to end	Day	67% 11% 6% 10% 5% 1	3575
January	1st to 10th	Night	79% 8% 7% 4 1	8769
	11th to 20th	Night	55% 10% 13% 10% 8% 4	8421
	21st to end	Night	58% 10% 16% 13% 4	8994
February	1st to 10th	Night	67% 7% 9% 9% 6% 1	2940
	11th to 20th	Night	62% 7% 13% 12% 6% 1	2581
	21st to end	Night	61% 7% 11% 13% 6% 1	1980
March	1st to 10th	Night	53% 7% 18% 12% 9%	5376
	11th to 20th	Night	51% 11% 17% 17% 4	5115
	21st to end	Night	68% 9% 13% 8% 2	5322
April	1st to 10th	Night	50% 10% 18% 15% 6%	1995
	11th to 20th	Night	49% 8% 17% 21% 5%	1781
	21st to end	Night	50% 8% 15% 22% 5% 1	1800
May	1st to 10th	Night	44% 5% 13% 26% 12%	3878
	11th to 20th	Night	46% 12% 17% 20% 6%	3304
	21st to end	Night	42% 9% 17% 25% 8%	3470
June	1st to 10th	Night	47% 9% 19% 19% 5%	1400
	11th to 20th	Night	49% 8% 17% 16% 9%	1400
	21st to end	Night	31% 10% 20% 27% 12% 1	1400
July	1st to 10th	Night	20% 9% 16% 24% 24% 6%	3145
	11th to 20th	Night	21% 7% 17% 28% 20% 7%	3138
	21st to end	Night	22% 7% 17% 25% 20% 8%	3844
August	1st to 10th	Night	27% 9% 15% 27% 19% 3	2601
	11th to 20th	Night	25% 7% 25% 29% 14% 1	2888
	21st to end	Night	24% 7% 21% 34% 14% 1	3245
September	1st to 10th	Night	25% 5% 18% 32% 15% 4	1973
	11th to 20th	Night	34% 8% 17% 28% 12% 1	2193
	21st to end	Night	36% 7% 22% 22% 12% 1	2200
October	1st to 10th	Night	30% 7% 22% 32% 9%	3664
	11th to 20th	Night	37% 7% 16% 30% 9%	4175
	21st to end	Night	49% 11% 18% 18% 4	4600
November	1st to 10th	Night	63% 9% 12% 11% 4 1	2676
	11th to 20th	Night	65% 9% 10% 11% 5%	3000
	21st to end	Night	65% 8% 12% 9% 5% 1	3150
December	1st to 10th	Night	62% 14% 14% 7% 2 1	5040
	11th to 20th	Night	75% 11% 8% 5% 1	5697
	21st to end	Night	71% 11% 8% 5% 4 1	7623

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	21% 20% 32% 17% 7% 3	220
	11th to 20th	Day	16% 17% 40% 22% 3 1	220
	21st to end	Day	14% 23% 42% 14% 5% 2	242
February	1st to 10th	Day	20% 24% 36% 13% 5% 1	220
	11th to 20th	Day	13% 21% 38% 22% 5% 1	334
	21st to end	Day	22% 27% 32% 15% 3	414
March	1st to 10th	Day	26% 26% 28% 13% 7% 1	500
	11th to 20th	Day	23% 23% 27% 19% 5% 2	500
	21st to end	Day	25% 30% 25% 13% 5% 1	550
April	1st to 10th	Day	26% 24% 28% 17% 4 1	500
	11th to 20th	Day	25% 26% 28% 13% 6% 1	492
	21st to end	Day	25% 21% 32% 13% 7% 2	500
May	1st to 10th	Day	24% 17% 30% 18% 8% 3	503
	11th to 20th	Day	24% 14% 25% 22% 12% 3	655
	21st to end	Day	25% 15% 23% 22% 13% 2	789
June	1st to 10th	Day	23% 21% 28% 17% 9% 1	730
	11th to 20th	Day	25% 21% 26% 18% 9% 1	730
	21st to end	Day	13% 18% 28% 25% 12% 3	730
July	1st to 10th	Day	11% 14% 28% 28% 15% 3	721
	11th to 20th	Day	12% 17% 31% 26% 13% 1	718
	21st to end	Day	9% 16% 37% 23% 12% 3	586
August	1st to 10th	Day	11% 17% 34% 25% 10% 3	527
	11th to 20th	Day	7% 19% 35% 25% 10% 4	517
	21st to end	Day	13% 21% 32% 20% 10% 3	583
September	1st to 10th	Day	17% 22% 28% 18% 10% 4	530
	11th to 20th	Day	16% 20% 33% 21% 8% 3	530
	21st to end	Day	27% 26% 26% 16% 4 1	530
October	1st to 10th	Day	23% 20% 28% 20% 7% 2	490
	11th to 20th	Day	28% 17% 26% 16% 11% 2	330
	21st to end	Day	30% 20% 27% 19% 4 1	363
November	1st to 10th	Day	29% 19% 29% 19% 2	330
	11th to 20th	Day	29% 21% 32% 14% 3 1	297
	21st to end	Day	20% 23% 30% 13% 9% 5%	220
December	1st to 10th	Day	25% 23% 26% 15% 8% 2	220
	11th to 20th	Day	22% 24% 35% 16% 2 1	220
	21st to end	Day	17% 19% 37% 21% 5% 1	242
January	1st to 10th	Night	17% 19% 41% 18% 4	1050
	11th to 20th	Night	12% 17% 44% 22% 4	911
	21st to end	Night	10% 16% 45% 23% 5% 1	924
February	1st to 10th	Night	14% 15% 41% 23% 7%	840
	11th to 20th	Night	11% 15% 41% 28% 5%	804
	21st to end	Night	14% 14% 35% 28% 8% 1	660
March	1st to 10th	Night	14% 18% 36% 24% 7% 1	800
	11th to 20th	Night	17% 18% 26% 28% 10% 1	800
	21st to end	Night	16% 16% 29% 29% 9% 2	880
April	1st to 10th	Night	15% 16% 25% 32% 11% 1	795
	11th to 20th	Night	15% 18% 29% 28% 10%	593
	21st to end	Night	15% 16% 27% 30% 12% 1	600
May	1st to 10th	Night	19% 13% 22% 32% 14% 1	511
	11th to 20th	Night	14% 10% 21% 32% 21% 3	394
	21st to end	Night	22% 9% 19% 28% 20% 1	433
June	1st to 10th	Night	18% 11% 22% 32% 16% 2	400
	11th to 20th	Night	21% 11% 26% 28% 14%	400
	21st to end	Night	11% 8% 21% 37% 23% 2	400
July	1st to 10th	Night	5% 7% 21% 41% 26% 1	390
	11th to 20th	Night	7% 7% 22% 44% 19% 1	388
	21st to end	Night	5% 9% 18% 42% 25% 1	438
August	1st to 10th	Night	7% 6% 16% 43% 27% 1	398
	11th to 20th	Night	7% 8% 19% 40% 25% 2	566
	21st to end	Night	10% 12% 21% 37% 18% 1	660
September	1st to 10th	Night	9% 9% 21% 35% 22% 4	773
	11th to 20th	Night	13% 9% 21% 33% 20% 5%	800
	21st to end	Night	16% 13% 26% 30% 12% 3	800
October	1st to 10th	Night	18% 11% 22% 36% 12% 1	800
	11th to 20th	Night	16% 13% 28% 31% 11% 1	800
	21st to end	Night	18% 16% 32% 28% 6%	880
November	1st to 10th	Night	24% 13% 35% 23% 5%	831
	11th to 20th	Night	22% 19% 35% 19% 4	1050
	21st to end	Night	16% 17% 37% 22% 6% 1	1050
December	1st to 10th	Night	17% 16% 39% 23% 5% 1	1050
	11th to 20th	Night	14% 20% 43% 19% 4	1050
	21st to end	Night	14% 18% 43% 21% 4	1155

Page generated at 2026-02-12 22:42:17. Version ac07

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