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 2025-02-25.

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%	111983
	Night	7% 9% 4 10% 6% 6% 5% 5% 6% 8% 34%	115331
Transparency	Day	46% 7% 16% 23% 8%	111724
	Night	47% 7% 15% 22% 9% 1	115236
Seeing	Day	13% 8% 27% 30% 17% 5%	15843
	Night	12% 6% 29% 35% 16% 2	25163

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	6% 10% 4 14% 9% 8% 6% 5% 7% 6% 25%	3179
	11th to 20th	Day	4 9% 3 9% 8% 8% 7% 8% 9% 7% 26%	3159
	21st to end	Day	7% 15% 4 10% 6% 5% 5% 4 6% 8% 30%	3568
February	1st to 10th	Day	8% 13% 4 14% 8% 7% 6% 4 6% 6% 23%	1670
	11th to 20th	Day	6% 13% 5% 12% 8% 5% 5% 5% 6% 8% 26%	1755
	21st to end	Day	4 13% 5% 11% 9% 6% 8% 5% 8% 9% 21%	1449
March	1st to 10th	Day	5% 12% 5% 11% 7% 7% 8% 6% 7% 7% 26%	3187
	11th to 20th	Day	5% 9% 5% 13% 5% 4 4 3 5% 10% 37%	3489
	21st to end	Day	7% 10% 5% 18% 8% 6% 5% 3 5% 6% 27%	3825
April	1st to 10th	Day	8% 12% 4 11% 7% 5% 6% 5% 6% 7% 31%	2365
	11th to 20th	Day	11% 12% 5% 10% 5% 4 5% 4 7% 6% 30%	2440
	21st to end	Day	13% 12% 4 7% 5% 4 5% 4 7% 9% 31%	2510
May	1st to 10th	Day	16% 12% 4 10% 6% 5% 5% 4 4 6% 28%	4456
	11th to 20th	Day	12% 12% 3 8% 6% 6% 6% 5% 6% 8% 27%	4694
	21st to end	Day	12% 7% 4 9% 6% 6% 7% 6% 7% 8% 28%	5161
June	1st to 10th	Day	15% 8% 3 7% 6% 6% 5% 5% 7% 7% 32%	2850
	11th to 20th	Day	18% 9% 3 9% 6% 5% 6% 5% 8% 8% 24%	2850
	21st to end	Day	11% 6% 2 5% 5% 5% 6% 6% 7% 10% 36%	2850
July	1st to 10th	Day	7% 5% 2 5% 4 4 5% 5% 7% 8% 48%	4740
	11th to 20th	Day	9% 5% 2 6% 4 5% 5% 4 6% 9% 44%	4740
	21st to end	Day	6% 5% 2 5% 4 4 5% 4 6% 10% 50%	5138
August	1st to 10th	Day	13% 5% 2 7% 4 4 5% 4 6% 7% 44%	4596
	11th to 20th	Day	7% 5% 2 5% 4 4 5% 5% 6% 11% 46%	4028
	21st to end	Day	8% 5% 2 6% 4 4 5% 4 7% 9% 47%	4521
September	1st to 10th	Day	10% 6% 2 6% 6% 5% 4 3 6% 7% 45%	2369
	11th to 20th	Day	15% 8% 3 7% 4 3 4 3 5% 6% 42%	2157
	21st to end	Day	9% 6% 3 5% 4 4 4 3 6% 8% 48%	2085
October	1st to 10th	Day	8% 9% 3 7% 5% 5% 4 4 5% 7% 42%	3170
	11th to 20th	Day	9% 8% 3 6% 4 4 4 4 6% 10% 40%	3077
	21st to end	Day	6% 8% 3 8% 5% 5% 5% 5% 6% 8% 42%	2922
November	1st to 10th	Day	11% 14% 5% 11% 7% 5% 5% 3 6% 7% 26%	1568
	11th to 20th	Day	6% 15% 6% 14% 8% 4 4 5% 6% 7% 26%	1585
	21st to end	Day	6% 13% 6% 11% 8% 6% 6% 4 6% 8% 28%	1400
December	1st to 10th	Day	8% 13% 5% 11% 6% 6% 7% 6% 7% 7% 23%	2290
	11th to 20th	Day	8% 14% 4 12% 8% 9% 8% 4 6% 7% 20%	2642
	21st to end	Day	3 8% 3 13% 8% 7% 5% 4 5% 7% 38%	3498
January	1st to 10th	Night	3 8% 4 14% 9% 10% 8% 7% 8% 8% 21%	6766
	11th to 20th	Night	3 10% 4 10% 8% 7% 7% 7% 7% 7% 30%	6739
	21st to end	Night	6% 12% 5% 11% 6% 6% 5% 4 6% 7% 33%	7430
February	1st to 10th	Night	5% 11% 4 13% 8% 7% 7% 6% 7% 8% 24%	2729
	11th to 20th	Night	6% 10% 4 10% 8% 7% 6% 6% 8% 8% 28%	2532
	21st to end	Night	4 9% 4 11% 8% 7% 6% 5% 7% 9% 30%	2099
March	1st to 10th	Night	5% 13% 5% 13% 7% 6% 5% 5% 6% 9% 26%	3684
	11th to 20th	Night	3 8% 4 11% 6% 5% 5% 5% 7% 9% 37%	3490
	21st to end	Night	6% 10% 4 14% 8% 6% 7% 5% 7% 8% 25%	3828
April	1st to 10th	Night	7% 11% 3 7% 6% 5% 6% 4 6% 8% 37%	1811
	11th to 20th	Night	8% 12% 4 10% 7% 6% 5% 4 7% 7% 28%	1691
	21st to end	Night	12% 11% 4 8% 5% 4 4 3 5% 8% 34%	1669
May	1st to 10th	Night	21% 12% 4 8% 5% 4 5% 4 4 6% 27%	2509
	11th to 20th	Night	12% 8% 3 7% 5% 5% 5% 5% 8% 9% 33%	2199
	21st to end	Night	13% 8% 3 9% 7% 6% 7% 5% 6% 8% 28%	2414
June	1st to 10th	Night	12% 8% 3 8% 6% 5% 6% 5% 7% 7% 32%	1330
	11th to 20th	Night	17% 9% 3 9% 6% 5% 5% 5% 5% 7% 27%	1330
	21st to end	Night	7% 6% 2 6% 6% 5% 6% 6% 7% 9% 39%	1330
July	1st to 10th	Night	8% 5% 2 5% 4 5% 5% 4 7% 8% 47%	2220
	11th to 20th	Night	6% 3 1 4 4 3 4 4 8% 10% 52%	2220
	21st to end	Night	6% 3 2 4 3 4 4 5% 5% 8% 54%	2414
August	1st to 10th	Night	11% 5% 2 5% 5% 4 5% 4 6% 8% 45%	2334
	11th to 20th	Night	8% 5% 2 6% 4 4 5% 4 6% 10% 47%	2811
	21st to end	Night	8% 5% 2 7% 4 4 4 3 7% 8% 48%	3146
September	1st to 10th	Night	9% 5% 2 7% 4 4 5% 4 5% 8% 47%	1810
	11th to 20th	Night	12% 6% 3 6% 3 3 4 3 5% 7% 47%	2020
	21st to end	Night	7% 7% 2 6% 4 4 5% 4 5% 8% 48%	2095
October	1st to 10th	Night	8% 7% 2 7% 4 5% 5% 4 7% 8% 42%	3800
	11th to 20th	Night	6% 6% 3 7% 5% 4 4 4 6% 9% 46%	3838
	21st to end	Night	7% 10% 3 8% 4 5% 4 4 6% 9% 38%	4604
November	1st to 10th	Night	12% 15% 4 8% 6% 5% 5% 4 6% 6% 30%	2730
	11th to 20th	Night	8% 11% 4 13% 9% 7% 5% 5% 5% 7% 26%	2811
	21st to end	Night	5% 12% 5% 13% 7% 6% 5% 4 6% 8% 30%	3000
December	1st to 10th	Night	8% 17% 6% 15% 8% 6% 6% 4 6% 6% 19%	4890
	11th to 20th	Night	7% 15% 5% 15% 9% 7% 6% 4 7% 7% 18%	5550
	21st to end	Night	2 7% 3 12% 8% 6% 5% 4 6% 7% 42%	7458

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	58% 5% 11% 20% 6%	3179
	11th to 20th	Day	51% 7% 13% 14% 14% 1	3180
	21st to end	Day	52% 6% 19% 18% 5%	3568
February	1st to 10th	Day	61% 6% 10% 17% 7%	1670
	11th to 20th	Day	54% 7% 12% 18% 10% 1	1764
	21st to end	Day	56% 7% 12% 18% 7%	1449
March	1st to 10th	Day	53% 7% 16% 17% 8%	3187
	11th to 20th	Day	44% 7% 22% 18% 9%	3490
	21st to end	Day	56% 8% 11% 19% 6%	3825
April	1st to 10th	Day	51% 7% 13% 20% 9% 1	2365
	11th to 20th	Day	51% 6% 13% 20% 9% 1	2440
	21st to end	Day	47% 8% 14% 20% 10% 1	2510
May	1st to 10th	Day	57% 5% 10% 22% 6%	4456
	11th to 20th	Day	51% 7% 11% 22% 9% 1	4698
	21st to end	Day	46% 11% 15% 18% 9%	5162
June	1st to 10th	Day	48% 8% 14% 21% 9% 1	2850
	11th to 20th	Day	54% 11% 14% 17% 4 1	2850
	21st to end	Day	40% 11% 19% 21% 8% 1	2850
July	1st to 10th	Day	32% 8% 20% 27% 13% 1	4666
	11th to 20th	Day	35% 7% 16% 31% 11%	4659
	21st to end	Day	30% 7% 19% 34% 11%	4976
August	1st to 10th	Day	38% 7% 17% 35% 3	4578
	11th to 20th	Day	31% 6% 24% 31% 7%	4067
	21st to end	Day	33% 6% 23% 31% 6%	4520
September	1st to 10th	Day	38% 7% 17% 26% 10% 3	2369
	11th to 20th	Day	44% 5% 17% 27% 7%	2157
	21st to end	Day	34% 7% 16% 29% 11% 2	2085
October	1st to 10th	Day	40% 5% 23% 26% 6%	3170
	11th to 20th	Day	39% 5% 16% 31% 9%	3077
	21st to end	Day	41% 5% 20% 29% 5%	2922
November	1st to 10th	Day	58% 5% 13% 18% 5% 1	1568
	11th to 20th	Day	56% 7% 16% 17% 4	1585
	21st to end	Day	53% 7% 17% 18% 4	1400
December	1st to 10th	Day	58% 7% 19% 12% 4	2290
	11th to 20th	Day	61% 6% 14% 15% 4	2644
	21st to end	Day	47% 4 9% 26% 13% 1	3498
January	1st to 10th	Night	56% 7% 14% 15% 8%	6766
	11th to 20th	Night	50% 5% 14% 15% 15% 1	6780
	21st to end	Night	50% 6% 17% 23% 4	7430
February	1st to 10th	Night	54% 7% 12% 17% 9% 1	2729
	11th to 20th	Night	50% 8% 13% 18% 12%	2533
	21st to end	Night	48% 8% 12% 23% 9% 1	2099
March	1st to 10th	Night	53% 7% 15% 19% 7%	3684
	11th to 20th	Night	41% 7% 21% 23% 8% 1	3490
	21st to end	Night	52% 9% 14% 19% 7%	3828
April	1st to 10th	Night	42% 8% 14% 21% 14% 1	1811
	11th to 20th	Night	52% 8% 11% 17% 11% 1	1691
	21st to end	Night	47% 6% 11% 21% 13% 2	1669
May	1st to 10th	Night	57% 5% 8% 22% 7%	2509
	11th to 20th	Night	42% 9% 13% 23% 13% 1	2199
	21st to end	Night	47% 13% 13% 21% 6% 1	2414
June	1st to 10th	Night	47% 8% 13% 23% 9% 1	1330
	11th to 20th	Night	53% 10% 12% 17% 8%	1330
	21st to end	Night	38% 10% 20% 25% 8% 1	1330
July	1st to 10th	Night	34% 7% 20% 21% 17% 1	2185
	11th to 20th	Night	26% 7% 18% 33% 15%	2178
	21st to end	Night	27% 6% 20% 33% 13% 1	2337
August	1st to 10th	Night	36% 7% 17% 36% 4	2327
	11th to 20th	Night	33% 7% 20% 32% 8%	2838
	21st to end	Night	33% 5% 19% 33% 9% 1	3146
September	1st to 10th	Night	34% 8% 18% 23% 12% 5%	1810
	11th to 20th	Night	37% 6% 15% 30% 10% 2	2020
	21st to end	Night	33% 7% 15% 30% 14% 2	2095
October	1st to 10th	Night	38% 6% 18% 29% 7% 1	3800
	11th to 20th	Night	34% 4 16% 36% 10%	3838
	21st to end	Night	42% 5% 20% 27% 5%	4604
November	1st to 10th	Night	54% 6% 13% 18% 8% 1	2730
	11th to 20th	Night	57% 6% 14% 16% 6% 1	2811
	21st to end	Night	51% 8% 18% 18% 5%	3000
December	1st to 10th	Night	65% 6% 12% 11% 4 1	4890
	11th to 20th	Night	64% 6% 15% 11% 4	5547
	21st to end	Night	42% 5% 13% 22% 16% 2	7458

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% 5% 34% 30% 17% 5%	200
	11th to 20th	Day	11% 6% 32% 28% 20% 4	200
	21st to end	Day	13% 9% 37% 27% 11% 3	220
February	1st to 10th	Day	11% 9% 34% 31% 12% 4	235
	11th to 20th	Day	10% 5% 33% 33% 15% 4	300
	21st to end	Day	8% 7% 30% 29% 21% 5%	237
March	1st to 10th	Day	12% 9% 30% 33% 14% 2	416
	11th to 20th	Day	10% 8% 36% 26% 14% 5%	460
	21st to end	Day	14% 7% 30% 30% 15% 4	506
April	1st to 10th	Day	12% 11% 38% 26% 9% 3	460
	11th to 20th	Day	14% 10% 28% 32% 13% 3	452
	21st to end	Day	17% 12% 30% 29% 10% 2	500
May	1st to 10th	Day	14% 9% 27% 29% 16% 4	653
	11th to 20th	Day	11% 8% 24% 32% 19% 6%	675
	21st to end	Day	17% 6% 21% 27% 21% 8%	734
June	1st to 10th	Day	16% 10% 25% 32% 13% 3	680
	11th to 20th	Day	18% 10% 26% 26% 14% 6%	680
	21st to end	Day	11% 6% 24% 28% 21% 9%	680
July	1st to 10th	Day	10% 4 18% 33% 26% 9%	671
	11th to 20th	Day	13% 5% 24% 28% 21% 9%	668
	21st to end	Day	9% 4 20% 29% 29% 8%	739
August	1st to 10th	Day	11% 5% 19% 30% 27% 9%	653
	11th to 20th	Day	9% 5% 23% 32% 22% 8%	477
	21st to end	Day	10% 7% 22% 31% 22% 8%	539
September	1st to 10th	Day	13% 6% 32% 28% 15% 5%	490
	11th to 20th	Day	21% 8% 24% 27% 15% 4	490
	21st to end	Day	12% 14% 28% 30% 14% 3	485
October	1st to 10th	Day	14% 8% 26% 34% 13% 5%	300
	11th to 20th	Day	15% 8% 32% 30% 13% 2	300
	21st to end	Day	11% 10% 38% 26% 12% 3	330
November	1st to 10th	Day	18% 7% 28% 33% 11% 2	300
	11th to 20th	Day	12% 8% 39% 30% 11% 1	293
	21st to end	Day	10% 8% 31% 35% 11% 5%	200
December	1st to 10th	Day	12% 5% 32% 31% 16% 5%	200
	11th to 20th	Day	11% 12% 30% 30% 18% 1	200
	21st to end	Day	10% 4 28% 31% 21% 6%	220
January	1st to 10th	Night	11% 7% 31% 38% 13% 2	1000
	11th to 20th	Night	9% 8% 33% 34% 14% 1	1000
	21st to end	Night	13% 10% 35% 30% 10% 1	1085
February	1st to 10th	Night	10% 7% 26% 38% 16% 3	800
	11th to 20th	Night	10% 7% 30% 34% 17% 2	784
	21st to end	Night	9% 3 23% 40% 21% 4	646
March	1st to 10th	Night	10% 6% 28% 39% 16% 2	760
	11th to 20th	Night	10% 5% 30% 38% 14% 3	760
	21st to end	Night	13% 5% 29% 35% 15% 3	836
April	1st to 10th	Night	12% 7% 29% 34% 17% 2	585
	11th to 20th	Night	15% 7% 28% 36% 13% 1	563
	21st to end	Night	17% 9% 24% 37% 14%	570
May	1st to 10th	Night	16% 5% 25% 35% 17% 3	552
	11th to 20th	Night	12% 6% 22% 41% 18% 2	374
	21st to end	Night	18% 5% 24% 29% 22% 2	411
June	1st to 10th	Night	17% 7% 25% 33% 16% 2	380
	11th to 20th	Night	21% 7% 21% 28% 21% 2	380
	21st to end	Night	10% 3 23% 35% 26% 3	380
July	1st to 10th	Night	10% 7% 16% 42% 25%	370
	11th to 20th	Night	11% 4 20% 41% 21% 4	368
	21st to end	Night	6% 6% 19% 39% 26% 4	416
August	1st to 10th	Night	9% 4 17% 37% 27% 6%	416
	11th to 20th	Night	13% 3 17% 41% 25% 2	564
	21st to end	Night	9% 4 24% 38% 24% 1	627
September	1st to 10th	Night	12% 3 22% 40% 20% 2	570
	11th to 20th	Night	14% 4 21% 43% 16% 1	690
	21st to end	Night	10% 5% 32% 35% 17% 1	760
October	1st to 10th	Night	13% 4 29% 36% 16% 1	760
	11th to 20th	Night	12% 5% 31% 36% 14% 2	760
	21st to end	Night	14% 6% 33% 36% 11% 1	921
November	1st to 10th	Night	18% 6% 32% 31% 11% 2	975
	11th to 20th	Night	15% 7% 33% 32% 10% 3	1000
	21st to end	Night	10% 6% 36% 35% 11% 1	1000
December	1st to 10th	Night	13% 7% 32% 28% 16% 4	1000
	11th to 20th	Night	13% 8% 36% 31% 12% 1	1000
	21st to end	Night	9% 4 32% 34% 18% 3	1100

Page generated at 2025-02-22 04:51:35. Version ac07

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