Dauphin
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Dauphin clear sky chart from 2005-11-06 to 2025-10-19.

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% 8% 3 8% 5% 5% 5% 4 6% 7% 37%	131015
	Night	9% 10% 4 10% 6% 5% 5% 4 6% 7% 34%	127499
Transparency	Day	44% 8% 15% 24% 8% 1	130725
	Night	48% 7% 13% 22% 9% 1	127370
Seeing	Day	16% 7% 28% 30% 15% 4	17654
	Night	16% 6% 27% 35% 15% 2	27526

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% 7% 15% 9% 8% 8% 5% 7% 7% 18%	3179
	11th to 20th	Day	4 9% 5% 13% 10% 9% 7% 11% 7% 5% 20%	3340
	21st to end	Day	4 14% 7% 11% 5% 5% 7% 4 6% 6% 31%	4004
February	1st to 10th	Day	8% 11% 4 11% 8% 7% 7% 6% 7% 6% 25%	1600
	11th to 20th	Day	6% 9% 4 9% 7% 8% 8% 5% 8% 6% 29%	1716
	21st to end	Day	6% 12% 5% 11% 8% 7% 5% 7% 4 6% 30%	1650
March	1st to 10th	Day	7% 13% 5% 9% 7% 7% 6% 4 6% 8% 29%	4500
	11th to 20th	Day	7% 12% 5% 11% 8% 5% 5% 4 5% 6% 30%	4838
	21st to end	Day	9% 10% 3 9% 6% 5% 5% 4 5% 6% 36%	5679
April	1st to 10th	Day	9% 11% 3 8% 5% 3 6% 4 6% 7% 38%	2415
	11th to 20th	Day	13% 12% 5% 9% 6% 4 4 3 5% 6% 32%	2572
	21st to end	Day	11% 8% 2 8% 6% 4 6% 4 6% 7% 39%	2600
May	1st to 10th	Day	14% 8% 3 6% 4 4 5% 4 6% 5% 41%	6242
	11th to 20th	Day	22% 9% 3 6% 5% 4 4 3 5% 7% 32%	6745
	21st to end	Day	16% 7% 2 5% 4 4 4 3 4 6% 47%	7428
June	1st to 10th	Day	17% 7% 2 6% 4 5% 5% 5% 6% 7% 37%	3000
	11th to 20th	Day	17% 7% 2 7% 5% 5% 6% 4 7% 7% 32%	3000
	21st to end	Day	14% 5% 3 6% 6% 5% 5% 4 7% 9% 37%	3000
July	1st to 10th	Day	8% 5% 2 7% 5% 5% 5% 4 8% 10% 43%	6800
	11th to 20th	Day	9% 5% 2 5% 4 4 4 4 7% 10% 45%	6800
	21st to end	Day	8% 5% 2 5% 4 4 5% 4 8% 10% 46%	7091
August	1st to 10th	Day	9% 5% 2 5% 4 5% 5% 5% 8% 9% 42%	4552
	11th to 20th	Day	9% 5% 2 5% 4 4 4 4 6% 9% 48%	4292
	21st to end	Day	12% 5% 2 5% 4 4 5% 4 7% 8% 45%	4675
September	1st to 10th	Day	12% 5% 2 6% 4 4 4 4 5% 9% 46%	2442
	11th to 20th	Day	16% 7% 2 7% 4 5% 4 3 6% 8% 38%	2224
	21st to end	Day	13% 6% 3 6% 4 3 4 4 5% 6% 46%	2200
October	1st to 10th	Day	12% 8% 3 6% 4 4 4 3 4 7% 45%	3456
	11th to 20th	Day	10% 8% 2 6% 4 4 5% 5% 7% 10% 37%	2904
	21st to end	Day	12% 12% 5% 9% 5% 5% 4 4 7% 8% 31%	3091
November	1st to 10th	Day	18% 17% 4 9% 6% 4 3 3 3 4 28%	1683
	11th to 20th	Day	9% 15% 5% 14% 6% 4 4 3 5% 6% 28%	1470
	21st to end	Day	10% 17% 5% 13% 7% 6% 5% 4 4 5% 25%	1400
December	1st to 10th	Day	7% 13% 6% 17% 9% 9% 7% 4 5% 6% 17%	2290
	11th to 20th	Day	8% 13% 5% 12% 7% 6% 6% 5% 6% 7% 25%	2639
	21st to end	Day	3 8% 4 15% 7% 4 4 4 5% 5% 40%	3498
January	1st to 10th	Night	4 12% 8% 17% 10% 8% 6% 5% 7% 5% 19%	6787
	11th to 20th	Night	4 11% 5% 14% 10% 11% 11% 7% 6% 4 17%	6576
	21st to end	Night	5% 15% 7% 14% 7% 6% 6% 4 5% 6% 26%	6974
February	1st to 10th	Night	9% 12% 4 12% 6% 7% 9% 5% 4 5% 28%	2800
	11th to 20th	Night	5% 9% 4 9% 7% 8% 7% 5% 7% 7% 33%	2587
	21st to end	Night	5% 10% 5% 13% 7% 6% 6% 4 4 6% 33%	1980
March	1st to 10th	Night	7% 14% 4 10% 6% 5% 4 4 6% 7% 32%	5374
	11th to 20th	Night	7% 15% 6% 10% 6% 4 4 3 5% 6% 34%	5125
	21st to end	Night	10% 11% 4 9% 6% 5% 5% 4 5% 6% 36%	5258
April	1st to 10th	Night	7% 10% 3 8% 6% 4 5% 4 6% 8% 39%	1985
	11th to 20th	Night	14% 11% 4 8% 4 5% 5% 4 5% 5% 34%	1779
	21st to end	Night	13% 10% 3 8% 5% 5% 5% 4 6% 7% 35%	1800
May	1st to 10th	Night	14% 9% 3 6% 4 3 4 4 5% 6% 41%	3735
	11th to 20th	Night	17% 8% 3 7% 5% 5% 5% 5% 6% 8% 32%	3169
	21st to end	Night	14% 7% 2 5% 3 3 4 3 4 5% 48%	3470
June	1st to 10th	Night	18% 7% 3 6% 4 4 4 4 5% 7% 39%	1400
	11th to 20th	Night	17% 6% 3 6% 4 4 5% 4 6% 8% 37%	1400
	21st to end	Night	13% 6% 2 6% 5% 4 6% 6% 6% 7% 38%	1400
July	1st to 10th	Night	6% 4 2 5% 4 4 4 4 7% 11% 50%	3180
	11th to 20th	Night	9% 4 2 6% 4 4 5% 3 6% 9% 49%	3180
	21st to end	Night	7% 3 2 5% 4 4 5% 4 6% 8% 53%	3771
August	1st to 10th	Night	12% 6% 3 5% 4 5% 4 4 5% 8% 45%	2608
	11th to 20th	Night	6% 5% 2 5% 4 5% 4 4 7% 10% 48%	2767
	21st to end	Night	12% 5% 2 5% 3 3 4 4 6% 9% 46%	3234
September	1st to 10th	Night	9% 4 2 5% 3 4 5% 4 6% 7% 51%	1955
	11th to 20th	Night	16% 7% 2 7% 4 3 5% 3 5% 6% 44%	2175
	21st to end	Night	12% 7% 2 6% 4 4 4 4 6% 6% 45%	2200
October	1st to 10th	Night	14% 7% 2 5% 3 3 3 3 5% 8% 48%	3674
	11th to 20th	Night	9% 8% 3 7% 4 5% 4 5% 7% 10% 38%	4202
	21st to end	Night	9% 11% 3 7% 4 4 5% 4 6% 8% 39%	4467
November	1st to 10th	Night	15% 16% 4 10% 6% 4 4 3 4 5% 28%	2613
	11th to 20th	Night	9% 18% 6% 13% 7% 5% 4 3 5% 5% 26%	2926
	21st to end	Night	10% 15% 6% 15% 7% 4 5% 3 4 5% 26%	3000
December	1st to 10th	Night	7% 16% 6% 18% 10% 9% 5% 3 4 5% 17%	4900
	11th to 20th	Night	7% 14% 5% 11% 8% 7% 6% 5% 6% 7% 24%	5568
	21st to end	Night	4 8% 4 16% 7% 6% 5% 4 6% 6% 34%	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	61% 9% 11% 16% 3	3179
	11th to 20th	Day	62% 6% 8% 17% 6%	3362
	21st to end	Day	51% 8% 15% 22% 4	4004
February	1st to 10th	Day	54% 9% 13% 15% 9% 1	1600
	11th to 20th	Day	50% 8% 13% 19% 10%	1725
	21st to end	Day	53% 6% 12% 19% 10%	1650
March	1st to 10th	Day	50% 8% 16% 17% 9%	4500
	11th to 20th	Day	51% 10% 14% 19% 7%	4840
	21st to end	Day	45% 8% 13% 23% 12%	5679
April	1st to 10th	Day	43% 9% 14% 21% 12% 1	2415
	11th to 20th	Day	53% 6% 11% 18% 11% 1	2572
	21st to end	Day	43% 10% 13% 23% 9% 1	2600
May	1st to 10th	Day	40% 7% 11% 26% 14% 2	6242
	11th to 20th	Day	50% 7% 12% 21% 8% 1	6749
	21st to end	Day	38% 8% 8% 21% 22% 4	7428
June	1st to 10th	Day	45% 10% 14% 22% 9% 1	3000
	11th to 20th	Day	47% 10% 17% 17% 9% 1	3000
	21st to end	Day	41% 10% 19% 24% 6% 1	3000
July	1st to 10th	Day	33% 10% 25% 27% 4	6726
	11th to 20th	Day	32% 8% 21% 35% 4	6719
	21st to end	Day	30% 9% 23% 30% 7% 1	6893
August	1st to 10th	Day	33% 11% 19% 28% 9%	4536
	11th to 20th	Day	31% 8% 22% 34% 5%	4334
	21st to end	Day	34% 8% 22% 29% 6%	4674
September	1st to 10th	Day	35% 8% 16% 29% 11% 1	2442
	11th to 20th	Day	45% 8% 16% 23% 8%	2224
	21st to end	Day	39% 8% 14% 29% 11%	2200
October	1st to 10th	Day	40% 5% 15% 33% 7%	3456
	11th to 20th	Day	38% 9% 14% 34% 5%	2904
	21st to end	Day	51% 7% 15% 20% 7%	3091
November	1st to 10th	Day	61% 5% 11% 17% 6% 1	1683
	11th to 20th	Day	57% 7% 14% 14% 6% 1	1470
	21st to end	Day	61% 7% 10% 18% 4	1400
December	1st to 10th	Day	67% 8% 12% 9% 3	2290
	11th to 20th	Day	55% 8% 17% 15% 4	2640
	21st to end	Day	45% 5% 13% 20% 14% 3	3498
January	1st to 10th	Night	63% 8% 9% 16% 5%	6787
	11th to 20th	Night	66% 7% 9% 14% 4	6616
	21st to end	Night	58% 8% 14% 16% 4	6974
February	1st to 10th	Night	55% 7% 11% 17% 8% 1	2800
	11th to 20th	Night	45% 8% 13% 22% 11% 1	2588
	21st to end	Night	51% 5% 12% 24% 9%	1980
March	1st to 10th	Night	49% 8% 13% 22% 8% 1	5374
	11th to 20th	Night	49% 6% 10% 21% 13% 1	5125
	21st to end	Night	47% 8% 8% 29% 8%	5258
April	1st to 10th	Night	42% 7% 14% 19% 17% 2	1985
	11th to 20th	Night	51% 6% 9% 21% 12% 2	1779
	21st to end	Night	46% 7% 12% 22% 10% 2	1800
May	1st to 10th	Night	40% 7% 12% 19% 20% 1	3735
	11th to 20th	Night	48% 7% 15% 20% 9% 1	3169
	21st to end	Night	36% 8% 10% 19% 24% 3	3470
June	1st to 10th	Night	45% 7% 14% 23% 11% 1	1400
	11th to 20th	Night	44% 8% 15% 21% 11% 1	1400
	21st to end	Night	40% 13% 18% 22% 7% 1	1400
July	1st to 10th	Night	27% 8% 26% 32% 7%	3145
	11th to 20th	Night	31% 7% 18% 40% 5%	3138
	21st to end	Night	27% 9% 23% 31% 10% 1	3664
August	1st to 10th	Night	36% 8% 18% 26% 13%	2600
	11th to 20th	Night	29% 8% 24% 30% 8% 1	2791
	21st to end	Night	33% 9% 18% 31% 8%	3234
September	1st to 10th	Night	30% 8% 16% 31% 14% 2	1955
	11th to 20th	Night	41% 7% 14% 28% 9% 1	2175
	21st to end	Night	38% 8% 11% 31% 11% 2	2200
October	1st to 10th	Night	35% 5% 14% 27% 17% 1	3674
	11th to 20th	Night	39% 7% 12% 32% 10% 1	4202
	21st to end	Night	43% 6% 16% 29% 6%	4467
November	1st to 10th	Night	58% 7% 12% 15% 6% 2	2613
	11th to 20th	Night	61% 7% 12% 15% 4	2926
	21st to end	Night	60% 7% 14% 14% 4	3000
December	1st to 10th	Night	69% 6% 10% 10% 4	4900
	11th to 20th	Night	56% 8% 14% 15% 7%	5566
	21st to end	Night	48% 7% 12% 18% 12% 3	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	12% 6% 30% 34% 14% 4	300
	11th to 20th	Day	12% 7% 27% 41% 10% 2	300
	21st to end	Day	15% 7% 30% 30% 15% 2	330
February	1st to 10th	Day	14% 6% 34% 34% 11% 1	300
	11th to 20th	Day	10% 6% 32% 32% 17% 4	300
	21st to end	Day	9% 9% 33% 30% 16% 2	249
March	1st to 10th	Day	16% 6% 24% 35% 17% 2	300
	11th to 20th	Day	15% 11% 29% 31% 12% 3	300
	21st to end	Day	17% 8% 28% 28% 17% 3	416
April	1st to 10th	Day	14% 11% 33% 28% 11% 3	515
	11th to 20th	Day	20% 8% 31% 29% 11% 2	690
	21st to end	Day	15% 9% 29% 33% 13% 2	700
May	1st to 10th	Day	15% 8% 29% 28% 18% 2	703
	11th to 20th	Day	21% 7% 29% 26% 14% 3	725
	21st to end	Day	22% 6% 21% 30% 18% 3	789
June	1st to 10th	Day	20% 11% 30% 23% 12% 5%	730
	11th to 20th	Day	19% 10% 28% 25% 13% 5%	730
	21st to end	Day	16% 6% 23% 35% 16% 4	730
July	1st to 10th	Day	11% 6% 23% 32% 21% 7%	721
	11th to 20th	Day	11% 5% 29% 31% 19% 5%	718
	21st to end	Day	10% 6% 25% 32% 20% 7%	794
August	1st to 10th	Day	10% 6% 26% 33% 19% 7%	726
	11th to 20th	Day	12% 5% 23% 29% 21% 9%	715
	21st to end	Day	16% 5% 23% 32% 21% 2	803
September	1st to 10th	Day	12% 8% 34% 28% 15% 3	572
	11th to 20th	Day	16% 10% 31% 27% 15% 2	354
	21st to end	Day	16% 6% 33% 30% 12% 3	330
October	1st to 10th	Day	24% 8% 28% 24% 14% 2	330
	11th to 20th	Day	23% 7% 33% 23% 12% 2	324
	21st to end	Day	22% 11% 28% 29% 6% 4	330
November	1st to 10th	Day	27% 10% 27% 24% 9% 3	300
	11th to 20th	Day	18% 9% 32% 28% 9% 3	300
	21st to end	Day	21% 11% 32% 26% 8% 1	300
December	1st to 10th	Day	13% 11% 29% 31% 14% 2	300
	11th to 20th	Day	15% 6% 38% 31% 9% 2	300
	21st to end	Day	12% 5% 26% 33% 20% 4	330
January	1st to 10th	Night	12% 8% 30% 37% 11% 2	1000
	11th to 20th	Night	15% 6% 31% 33% 13% 2	1000
	21st to end	Night	15% 6% 33% 34% 11% 1	1100
February	1st to 10th	Night	15% 5% 29% 35% 14% 2	1000
	11th to 20th	Night	8% 6% 28% 40% 15% 2	974
	21st to end	Night	10% 5% 25% 39% 19% 3	660
March	1st to 10th	Night	16% 6% 24% 37% 16% 2	800
	11th to 20th	Night	12% 8% 28% 36% 15% 1	667
	21st to end	Night	18% 5% 26% 33% 14% 3	660
April	1st to 10th	Night	11% 9% 22% 42% 15% 1	600
	11th to 20th	Night	19% 7% 25% 36% 13%	593
	21st to end	Night	17% 7% 27% 36% 14%	600
May	1st to 10th	Night	19% 6% 23% 37% 14% 1	600
	11th to 20th	Night	17% 8% 24% 32% 18% 1	591
	21st to end	Night	23% 5% 17% 39% 15% 1	650
June	1st to 10th	Night	19% 6% 26% 32% 16% 2	600
	11th to 20th	Night	20% 3 25% 36% 14% 2	600
	21st to end	Night	14% 5% 24% 38% 19%	600
July	1st to 10th	Night	8% 3 22% 43% 23% 1	585
	11th to 20th	Night	10% 4 25% 40% 20% 2	582
	21st to end	Night	10% 4 19% 42% 22% 4	657
August	1st to 10th	Night	11% 4 22% 40% 21% 2	597
	11th to 20th	Night	11% 4 20% 36% 26% 3	594
	21st to end	Night	16% 4 22% 37% 20% 1	660
September	1st to 10th	Night	12% 6% 22% 39% 19% 2	600
	11th to 20th	Night	19% 7% 22% 40% 12% 1	600
	21st to end	Night	14% 5% 30% 37% 13% 2	600
October	1st to 10th	Night	22% 5% 26% 36% 11%	645
	11th to 20th	Night	20% 9% 25% 33% 13% 1	991
	21st to end	Night	19% 10% 30% 30% 10% 1	1045
November	1st to 10th	Night	23% 8% 30% 27% 11% 1	975
	11th to 20th	Night	17% 7% 35% 31% 8% 2	1000
	21st to end	Night	17% 8% 34% 31% 8% 1	1000
December	1st to 10th	Night	13% 9% 28% 33% 14% 3	1000
	11th to 20th	Night	17% 8% 31% 30% 13% 2	1000
	21st to end	Night	15% 5% 25% 35% 18% 3	1100

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