Wainwright
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Wainwright clear sky chart from 2005-11-06 to 2026-07-01.

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	9% 9% 3 9% 6% 5% 5% 4 6% 8% 35%	142003
	Night	7% 9% 4 10% 6% 6% 5% 5% 6% 8% 34%	139073
Transparency	Day	46% 6% 15% 24% 8% 1	141700
	Night	47% 6% 15% 22% 10% 1	138962
Seeing	Day	13% 8% 27% 29% 17% 5%	17736
	Night	12% 6% 29% 35% 16% 2	26823

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	8% 11% 5% 13% 9% 8% 6% 5% 6% 6% 23%	4125
	11th to 20th	Day	3 8% 3 10% 8% 8% 7% 7% 9% 8% 30%	4119
	21st to end	Day	6% 12% 4 9% 9% 6% 5% 4 7% 8% 30%	4628
February	1st to 10th	Day	8% 13% 4 14% 8% 7% 6% 4 6% 6% 25%	1754
	11th to 20th	Day	6% 13% 5% 12% 7% 5% 5% 5% 7% 8% 26%	1845
	21st to end	Day	4 13% 5% 12% 9% 6% 8% 5% 8% 9% 22%	1557
March	1st to 10th	Day	4 11% 4 12% 7% 6% 6% 5% 7% 9% 29%	4693
	11th to 20th	Day	6% 10% 6% 16% 7% 5% 4 3 5% 9% 30%	5109
	21st to end	Day	9% 13% 6% 16% 7% 5% 5% 3 5% 6% 25%	5607
April	1st to 10th	Day	7% 12% 4 11% 6% 5% 6% 4 6% 7% 33%	2614
	11th to 20th	Day	11% 12% 5% 10% 5% 4 5% 4 7% 7% 30%	2700
	21st to end	Day	13% 12% 4 7% 5% 4 5% 4 7% 9% 31%	2774
May	1st to 10th	Day	10% 7% 3 8% 5% 5% 5% 4 6% 7% 40%	8275
	11th to 20th	Day	18% 11% 3 8% 6% 5% 5% 4 6% 7% 25%	8755
	21st to end	Day	11% 6% 2 8% 5% 6% 6% 5% 6% 7% 38%	9649
June	1st to 10th	Day	14% 8% 3 7% 6% 6% 5% 5% 7% 7% 32%	3150
	11th to 20th	Day	17% 9% 3 9% 6% 6% 6% 5% 8% 8% 23%	3150
	21st to end	Day	12% 6% 2 5% 5% 5% 6% 6% 7% 9% 35%	3150
July	1st to 10th	Day	7% 4 2 5% 4 4 5% 5% 7% 9% 47%	6781
	11th to 20th	Day	13% 6% 2 6% 4 5% 5% 4 6% 8% 41%	6780
	21st to end	Day	7% 5% 2 6% 4 5% 5% 4 6% 9% 45%	7376
August	1st to 10th	Day	12% 5% 2 7% 4 4 5% 4 6% 7% 44%	4743
	11th to 20th	Day	7% 5% 2 5% 4 4 5% 5% 6% 11% 46%	4158
	21st to end	Day	8% 5% 2 5% 4 4 5% 4 7% 9% 47%	4664
September	1st to 10th	Day	9% 6% 2 6% 5% 5% 4 3 6% 7% 45%	2493
	11th to 20th	Day	14% 8% 3 7% 4 4 4 3 5% 6% 44%	2270
	21st to end	Day	9% 6% 3 5% 4 4 4 3 6% 8% 49%	2195
October	1st to 10th	Day	7% 9% 3 7% 5% 5% 4 4 5% 7% 43%	3270
	11th to 20th	Day	9% 8% 3 6% 4 4 4 4 6% 10% 40%	3175
	21st to end	Day	6% 8% 3 8% 5% 5% 4 5% 5% 8% 42%	3015
November	1st to 10th	Day	11% 15% 5% 10% 6% 5% 5% 3 6% 7% 27%	1648
	11th to 20th	Day	6% 15% 5% 13% 8% 4 5% 5% 6% 7% 28%	1664
	21st to end	Day	6% 12% 5% 12% 8% 6% 6% 4 6% 8% 28%	1470
December	1st to 10th	Day	8% 13% 5% 12% 7% 7% 7% 6% 7% 7% 23%	2360
	11th to 20th	Day	8% 14% 4 12% 8% 9% 8% 4 6% 7% 20%	2712
	21st to end	Day	3 8% 3 13% 8% 7% 5% 4 5% 7% 37%	3575
January	1st to 10th	Night	7% 9% 4 14% 8% 9% 7% 6% 7% 7% 21%	8768
	11th to 20th	Night	3 8% 4 10% 7% 6% 7% 6% 7% 8% 34%	8779
	21st to end	Night	6% 11% 4 11% 7% 7% 5% 4 7% 8% 30%	9608
February	1st to 10th	Night	5% 11% 4 13% 8% 6% 7% 6% 7% 8% 25%	2865
	11th to 20th	Night	6% 10% 4 10% 8% 7% 6% 6% 8% 8% 28%	2662
	21st to end	Night	4 10% 4 11% 8% 7% 6% 6% 6% 8% 30%	2249
March	1st to 10th	Night	4 11% 5% 12% 7% 5% 6% 5% 7% 10% 29%	5416
	11th to 20th	Night	3 9% 5% 13% 7% 7% 6% 5% 6% 8% 30%	5110
	21st to end	Night	9% 13% 5% 14% 7% 5% 5% 4 6% 6% 25%	5610
April	1st to 10th	Night	6% 11% 3 7% 6% 5% 6% 4 7% 8% 37%	2002
	11th to 20th	Night	8% 12% 4 10% 7% 6% 6% 5% 7% 8% 28%	1871
	21st to end	Night	12% 11% 4 8% 4 4 4 3 5% 8% 35%	1845
May	1st to 10th	Night	12% 8% 3 7% 4 4 5% 4 5% 7% 42%	4666
	11th to 20th	Night	15% 10% 4 8% 5% 5% 5% 5% 7% 8% 28%	4105
	21st to end	Night	12% 6% 2 7% 6% 5% 7% 5% 7% 9% 34%	4522
June	1st to 10th	Night	13% 8% 3 8% 6% 5% 6% 5% 7% 7% 32%	1470
	11th to 20th	Night	17% 9% 3 10% 6% 6% 6% 5% 5% 7% 27%	1470
	21st to end	Night	9% 6% 2 7% 6% 5% 5% 5% 7% 8% 39%	1470
July	1st to 10th	Night	6% 4 2 5% 4 4 5% 4 8% 9% 50%	3180
	11th to 20th	Night	9% 4 2 6% 4 3 5% 4 7% 9% 47%	3180
	21st to end	Night	7% 4 2 6% 5% 5% 5% 5% 6% 8% 48%	3467
August	1st to 10th	Night	11% 5% 2 5% 5% 4 5% 4 6% 8% 45%	2407
	11th to 20th	Night	7% 5% 2 6% 4 4 5% 4 6% 10% 46%	2901
	21st to end	Night	8% 5% 2 7% 4 4 4 3 7% 8% 48%	3245
September	1st to 10th	Night	9% 5% 2 6% 4 4 5% 4 5% 8% 48%	1906
	11th to 20th	Night	11% 6% 3 6% 3 3 4 3 5% 7% 47%	2127
	21st to end	Night	7% 7% 1 6% 4 4 5% 4 5% 8% 48%	2205
October	1st to 10th	Night	8% 7% 2 7% 4 5% 5% 4 7% 8% 42%	3920
	11th to 20th	Night	6% 6% 3 7% 5% 4 4 4 6% 9% 46%	3960
	21st to end	Night	7% 10% 3 8% 4 5% 4 4 6% 9% 39%	4752
November	1st to 10th	Night	12% 15% 4 9% 6% 5% 5% 4 6% 6% 30%	2870
	11th to 20th	Night	8% 11% 4 13% 9% 7% 5% 5% 5% 7% 27%	2952
	21st to end	Night	5% 12% 5% 12% 7% 6% 5% 4 6% 8% 30%	3150
December	1st to 10th	Night	8% 17% 6% 15% 8% 6% 6% 4 6% 6% 19%	5040
	11th to 20th	Night	7% 15% 5% 15% 9% 7% 6% 5% 7% 7% 18%	5700
	21st to end	Night	2 7% 3 12% 8% 6% 5% 4 6% 7% 41%	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	61% 4 10% 17% 9%	4125
	11th to 20th	Day	47% 6% 15% 16% 16%	4140
	21st to end	Day	51% 6% 19% 18% 6%	4629
February	1st to 10th	Day	59% 5% 11% 17% 8%	1754
	11th to 20th	Day	53% 7% 12% 19% 9%	1854
	21st to end	Day	55% 6% 12% 19% 7%	1557
March	1st to 10th	Day	51% 5% 19% 19% 6%	4693
	11th to 20th	Day	52% 6% 16% 18% 8%	5110
	21st to end	Day	58% 6% 11% 20% 6%	5607
April	1st to 10th	Day	50% 6% 14% 20% 9% 1	2614
	11th to 20th	Day	51% 6% 13% 21% 9% 1	2700
	21st to end	Day	48% 8% 13% 21% 10% 1	2774
May	1st to 10th	Day	43% 4 9% 27% 15% 3	8275
	11th to 20th	Day	55% 5% 8% 22% 9%	8759
	21st to end	Day	41% 7% 15% 26% 10% 1	9650
June	1st to 10th	Day	47% 8% 13% 21% 10% 1	3150
	11th to 20th	Day	54% 10% 14% 17% 4 1	3150
	21st to end	Day	41% 10% 18% 22% 8% 1	3150
July	1st to 10th	Day	32% 6% 23% 29% 10%	6707
	11th to 20th	Day	40% 6% 14% 31% 9%	6699
	21st to end	Day	35% 6% 20% 31% 8%	7169
August	1st to 10th	Day	39% 7% 17% 34% 4	4725
	11th to 20th	Day	32% 6% 24% 30% 7%	4197
	21st to end	Day	33% 6% 23% 31% 6%	4663
September	1st to 10th	Day	37% 6% 17% 27% 10% 3	2493
	11th to 20th	Day	42% 5% 17% 28% 8%	2270
	21st to end	Day	33% 7% 17% 29% 11% 2	2195
October	1st to 10th	Day	40% 5% 22% 26% 7%	3270
	11th to 20th	Day	39% 5% 15% 32% 9%	3175
	21st to end	Day	40% 5% 20% 30% 5%	3015
November	1st to 10th	Day	57% 5% 12% 19% 6% 1	1648
	11th to 20th	Day	54% 7% 17% 18% 5%	1664
	21st to end	Day	53% 7% 16% 18% 5%	1470
December	1st to 10th	Day	58% 7% 19% 12% 4	2360
	11th to 20th	Day	61% 6% 14% 15% 3	2714
	21st to end	Day	47% 3 9% 26% 13% 1	3575
January	1st to 10th	Night	58% 6% 12% 13% 11%	8769
	11th to 20th	Night	46% 4 18% 17% 14% 1	8820
	21st to end	Night	51% 6% 17% 19% 7%	9608
February	1st to 10th	Night	53% 7% 13% 17% 9% 1	2865
	11th to 20th	Night	50% 8% 12% 18% 12%	2663
	21st to end	Night	49% 8% 12% 22% 9% 1	2249
March	1st to 10th	Night	49% 5% 19% 19% 7%	5416
	11th to 20th	Night	50% 6% 16% 21% 7%	5110
	21st to end	Night	57% 7% 10% 18% 9%	5610
April	1st to 10th	Night	42% 7% 15% 21% 14% 1	2002
	11th to 20th	Night	51% 7% 12% 17% 12% 1	1871
	21st to end	Night	46% 5% 11% 23% 13% 2	1845
May	1st to 10th	Night	42% 4 6% 27% 19% 2	4666
	11th to 20th	Night	50% 6% 12% 22% 10%	4105
	21st to end	Night	43% 8% 15% 24% 9% 1	4526
June	1st to 10th	Night	47% 7% 12% 22% 10% 1	1470
	11th to 20th	Night	54% 9% 12% 17% 8%	1470
	21st to end	Night	39% 9% 20% 25% 7% 1	1470
July	1st to 10th	Night	29% 6% 24% 28% 13%	3145
	11th to 20th	Night	34% 6% 15% 32% 12%	3138
	21st to end	Night	33% 6% 20% 30% 10% 1	3369
August	1st to 10th	Night	36% 7% 17% 35% 4	2400
	11th to 20th	Night	33% 7% 20% 31% 8%	2928
	21st to end	Night	33% 5% 19% 33% 10% 1	3245
September	1st to 10th	Night	33% 8% 18% 25% 12% 5%	1906
	11th to 20th	Night	36% 6% 15% 31% 10% 2	2127
	21st to end	Night	33% 6% 14% 31% 13% 2	2205
October	1st to 10th	Night	38% 6% 18% 29% 8% 1	3920
	11th to 20th	Night	34% 4 16% 36% 10%	3960
	21st to end	Night	42% 5% 20% 28% 5%	4752
November	1st to 10th	Night	55% 6% 13% 18% 8% 1	2870
	11th to 20th	Night	56% 6% 14% 16% 6% 1	2952
	21st to end	Night	51% 8% 17% 18% 6%	3150
December	1st to 10th	Night	66% 5% 12% 11% 4 1	5040
	11th to 20th	Night	64% 6% 15% 11% 4	5697
	21st to end	Night	43% 5% 13% 22% 15% 2	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	12% 5% 33% 30% 15% 5%	220
	11th to 20th	Day	11% 8% 32% 26% 19% 4	220
	21st to end	Day	13% 10% 36% 29% 11% 2	242
February	1st to 10th	Day	11% 8% 34% 31% 12% 4	259
	11th to 20th	Day	10% 5% 32% 33% 15% 4	330
	21st to end	Day	9% 7% 34% 28% 18% 4	273
March	1st to 10th	Day	12% 10% 31% 31% 14% 2	492
	11th to 20th	Day	11% 8% 36% 26% 14% 4	540
	21st to end	Day	15% 7% 31% 29% 14% 3	594
April	1st to 10th	Day	12% 10% 37% 28% 10% 3	540
	11th to 20th	Day	14% 11% 30% 30% 12% 2	532
	21st to end	Day	17% 10% 28% 29% 12% 3	584
May	1st to 10th	Day	13% 10% 28% 29% 15% 4	753
	11th to 20th	Day	14% 7% 24% 30% 19% 6%	775
	21st to end	Day	17% 6% 22% 28% 20% 7%	844
June	1st to 10th	Day	18% 10% 27% 30% 13% 3	780
	11th to 20th	Day	17% 9% 26% 27% 14% 6%	780
	21st to end	Day	13% 6% 23% 28% 20% 9%	780
July	1st to 10th	Day	10% 5% 19% 33% 26% 8%	722
	11th to 20th	Day	14% 5% 24% 28% 21% 9%	718
	21st to end	Day	9% 4 20% 30% 30% 8%	794
August	1st to 10th	Day	11% 5% 18% 30% 26% 10%	702
	11th to 20th	Day	9% 5% 24% 32% 22% 8%	517
	21st to end	Day	10% 7% 21% 31% 23% 8%	583
September	1st to 10th	Day	12% 7% 31% 28% 16% 6%	530
	11th to 20th	Day	19% 7% 23% 28% 17% 5%	530
	21st to end	Day	12% 13% 28% 30% 14% 2	525
October	1st to 10th	Day	12% 8% 27% 35% 15% 4	330
	11th to 20th	Day	15% 10% 31% 30% 12% 2	330
	21st to end	Day	11% 12% 39% 25% 11% 3	363
November	1st to 10th	Day	18% 8% 30% 31% 10% 2	330
	11th to 20th	Day	11% 9% 38% 30% 11% 1	322
	21st to end	Day	10% 7% 31% 35% 11% 5%	220
December	1st to 10th	Day	12% 6% 34% 29% 14% 5%	220
	11th to 20th	Day	10% 13% 31% 29% 16%	220
	21st to end	Day	10% 5% 29% 31% 19% 5%	242
January	1st to 10th	Night	11% 7% 31% 38% 12% 2	1050
	11th to 20th	Night	10% 9% 34% 33% 13% 1	1050
	21st to end	Night	13% 10% 35% 30% 10% 1	1139
February	1st to 10th	Night	10% 7% 27% 38% 16% 3	840
	11th to 20th	Night	11% 7% 30% 34% 17% 2	824
	21st to end	Night	9% 3 25% 39% 20% 4	692
March	1st to 10th	Night	10% 6% 28% 39% 15% 2	840
	11th to 20th	Night	10% 5% 31% 38% 14% 2	840
	21st to end	Night	14% 5% 30% 33% 15% 3	924
April	1st to 10th	Night	12% 7% 29% 35% 16% 2	647
	11th to 20th	Night	15% 6% 30% 35% 12% 1	623
	21st to end	Night	17% 9% 23% 38% 14%	630
May	1st to 10th	Night	15% 6% 25% 36% 16% 2	610
	11th to 20th	Night	13% 7% 22% 39% 17% 2	414
	21st to end	Night	18% 6% 23% 30% 22% 2	455
June	1st to 10th	Night	17% 8% 25% 32% 15% 2	420
	11th to 20th	Night	20% 6% 22% 28% 21% 2	420
	21st to end	Night	12% 3 21% 36% 25% 4	420
July	1st to 10th	Night	9% 6% 17% 43% 24%	390
	11th to 20th	Night	11% 4 20% 41% 20% 3	388
	21st to end	Night	6% 6% 19% 39% 26% 4	438
August	1st to 10th	Night	10% 4 17% 37% 28% 5%	438
	11th to 20th	Night	12% 3 18% 41% 24% 2	594
	21st to end	Night	9% 4 23% 39% 24% 1	660
September	1st to 10th	Night	12% 3 22% 41% 20% 2	600
	11th to 20th	Night	13% 4 20% 44% 18% 1	727
	21st to end	Night	10% 6% 33% 35% 17% 1	800
October	1st to 10th	Night	13% 5% 29% 37% 15% 1	800
	11th to 20th	Night	12% 5% 33% 36% 14% 2	800
	21st to end	Night	14% 7% 33% 36% 10% 1	970
November	1st to 10th	Night	18% 7% 33% 30% 10% 1	1025
	11th to 20th	Night	15% 7% 34% 32% 10% 3	1050
	21st to end	Night	10% 6% 36% 36% 12% 1	1050
December	1st to 10th	Night	13% 8% 33% 28% 16% 3	1050
	11th to 20th	Night	13% 8% 36% 30% 12% 1	1050
	21st to end	Night	9% 4 32% 34% 17% 3	1155

Page generated at 2026-06-28 00:10:42. Version ac07

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