The Pas
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the The Pas clear sky chart from 2005-11-06 to 2026-01-17.

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	10% 9% 4 9% 6% 5% 5% 4 6% 7% 34%	131718
	Night	9% 11% 4 11% 6% 6% 5% 4 6% 6% 31%	128682
Transparency	Day	49% 4 14% 24% 9% 1	131408
	Night	53% 3 13% 22% 9% 1	128574
Seeing	Day	18% 11% 31% 26% 12% 3	17674
	Night	17% 8% 30% 30% 12% 2	27186

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% 8% 22% 10% 7% 5% 5% 6% 4 13%	2779
	11th to 20th	Day	4 11% 6% 20% 9% 9% 7% 6% 9% 4 14%	3027
	21st to end	Day	6% 18% 7% 12% 7% 6% 6% 5% 7% 7% 18%	3986
February	1st to 10th	Day	7% 11% 4 12% 7% 7% 9% 8% 8% 7% 19%	1600
	11th to 20th	Day	5% 10% 4 10% 7% 7% 9% 7% 7% 7% 27%	1603
	21st to end	Day	5% 10% 6% 12% 9% 8% 7% 5% 6% 7% 26%	1650
March	1st to 10th	Day	5% 11% 5% 14% 8% 7% 6% 5% 6% 7% 27%	4500
	11th to 20th	Day	7% 10% 4 14% 7% 7% 6% 4 5% 6% 29%	4731
	21st to end	Day	4 9% 4 10% 5% 5% 6% 4 6% 6% 41%	5824
April	1st to 10th	Day	8% 9% 3 8% 5% 5% 5% 4 6% 7% 38%	2410
	11th to 20th	Day	11% 12% 4 9% 6% 5% 5% 3 5% 6% 35%	2572
	21st to end	Day	8% 8% 4 8% 7% 5% 6% 4 6% 7% 37%	2700
May	1st to 10th	Day	13% 10% 3 7% 5% 4 4 3 5% 6% 39%	6472
	11th to 20th	Day	18% 9% 3 7% 5% 4 5% 4 6% 8% 31%	6755
	21st to end	Day	14% 9% 3 6% 4 4 4 3 5% 5% 44%	7428
June	1st to 10th	Day	17% 10% 3 7% 5% 5% 5% 5% 5% 7% 30%	3176
	11th to 20th	Day	18% 8% 3 8% 5% 5% 5% 5% 7% 7% 30%	3200
	21st to end	Day	15% 8% 3 6% 6% 5% 6% 5% 6% 7% 33%	3200
July	1st to 10th	Day	9% 5% 2 6% 4 4 5% 4 7% 8% 47%	7240
	11th to 20th	Day	8% 4 2 5% 4 4 5% 5% 7% 8% 47%	7119
	21st to end	Day	8% 5% 2 6% 4 4 5% 4 7% 10% 43%	7297
August	1st to 10th	Day	11% 5% 2 7% 5% 5% 5% 3 6% 8% 43%	4552
	11th to 20th	Day	11% 5% 2 6% 4 4 5% 5% 7% 9% 42%	4466
	21st to end	Day	14% 7% 2 7% 5% 4 4 4 6% 9% 38%	4675
September	1st to 10th	Day	14% 6% 2 7% 5% 6% 5% 4 6% 9% 36%	2433
	11th to 20th	Day	17% 9% 3 8% 4 5% 4 4 5% 8% 33%	2280
	21st to end	Day	12% 8% 3 8% 5% 3 4 3 5% 8% 42%	2200
October	1st to 10th	Day	14% 10% 3 6% 4 4 5% 4 8% 8% 33%	3349
	11th to 20th	Day	10% 12% 4 8% 6% 6% 5% 4 6% 8% 31%	2922
	21st to end	Day	12% 17% 5% 10% 6% 5% 6% 4 5% 6% 22%	3190
November	1st to 10th	Day	15% 19% 6% 12% 6% 5% 5% 3 4 5% 18%	1632
	11th to 20th	Day	12% 16% 5% 15% 9% 6% 5% 4 4 6% 20%	1470
	21st to end	Day	7% 16% 8% 16% 10% 5% 6% 4 4 5% 19%	1470
December	1st to 10th	Day	9% 15% 7% 16% 10% 10% 7% 4 4 5% 12%	2360
	11th to 20th	Day	6% 15% 5% 11% 7% 6% 8% 5% 6% 9% 22%	2392
	21st to end	Day	5% 12% 6% 15% 6% 6% 5% 3 6% 6% 29%	3058
January	1st to 10th	Night	4 13% 8% 18% 10% 8% 7% 5% 5% 5% 17%	7386
	11th to 20th	Night	5% 11% 6% 19% 10% 8% 9% 8% 9% 4 11%	7015
	21st to end	Night	7% 18% 7% 15% 7% 7% 6% 5% 5% 5% 19%	6977
February	1st to 10th	Night	6% 12% 4 11% 8% 10% 8% 5% 6% 6% 24%	2800
	11th to 20th	Night	4 10% 4 11% 8% 7% 7% 6% 7% 6% 30%	2697
	21st to end	Night	4 9% 4 12% 9% 5% 7% 5% 5% 8% 31%	1985
March	1st to 10th	Night	6% 13% 4 10% 5% 5% 5% 4 5% 7% 35%	5374
	11th to 20th	Night	7% 10% 4 12% 8% 6% 4 4 6% 7% 32%	5238
	21st to end	Night	4 8% 3 8% 4 4 5% 4 6% 7% 46%	5121
April	1st to 10th	Night	9% 10% 3 8% 5% 5% 4 4 6% 7% 40%	1990
	11th to 20th	Night	11% 11% 4 8% 5% 5% 4 4 6% 6% 36%	1779
	21st to end	Night	7% 9% 4 8% 6% 6% 5% 4 5% 6% 40%	1696
May	1st to 10th	Night	13% 7% 3 7% 4 5% 4 4 5% 7% 41%	3507
	11th to 20th	Night	16% 8% 3 7% 5% 5% 6% 4 7% 8% 30%	3161
	21st to end	Night	14% 9% 2 8% 4 3 3 3 3 6% 45%	3470
June	1st to 10th	Night	17% 6% 2 6% 4 4 4 5% 7% 7% 38%	1220
	11th to 20th	Night	17% 7% 3 6% 5% 5% 5% 4 6% 8% 35%	1200
	21st to end	Night	14% 7% 3 7% 4 4 5% 5% 7% 7% 36%	1200
July	1st to 10th	Night	6% 5% 2 4 4 5% 6% 5% 7% 9% 47%	2720
	11th to 20th	Night	6% 4 2 4 4 4 4 3 6% 8% 54%	2844
	21st to end	Night	8% 5% 2 5% 4 5% 5% 4 8% 10% 45%	3555
August	1st to 10th	Night	8% 4 2 4 3 4 4 4 6% 8% 54%	2608
	11th to 20th	Night	10% 5% 2 5% 4 4 4 4 7% 10% 44%	2592
	21st to end	Night	14% 5% 2 6% 4 4 4 4 6% 8% 44%	3234
September	1st to 10th	Night	11% 6% 2 6% 3 5% 5% 4 6% 8% 45%	1965
	11th to 20th	Night	17% 7% 2 7% 4 4 4 4 6% 7% 38%	2119
	21st to end	Night	13% 7% 3 6% 4 5% 4 3 5% 7% 43%	2200
October	1st to 10th	Night	10% 8% 3 6% 4 5% 4 4 5% 7% 44%	3801
	11th to 20th	Night	9% 11% 4 9% 5% 4 5% 4 6% 8% 35%	4227
	21st to end	Night	14% 15% 4 10% 5% 6% 5% 4 5% 6% 26%	4610
November	1st to 10th	Night	14% 19% 6% 13% 6% 5% 3 3 4 5% 21%	2884
	11th to 20th	Night	11% 15% 6% 12% 9% 7% 4 3 5% 6% 21%	3150
	21st to end	Night	8% 17% 6% 15% 9% 7% 4 3 5% 5% 20%	3150
December	1st to 10th	Night	8% 19% 7% 17% 10% 10% 6% 3 4 4 12%	5050
	11th to 20th	Night	7% 13% 5% 12% 7% 6% 7% 7% 7% 6% 22%	6017
	21st to end	Night	5% 13% 6% 15% 8% 5% 5% 4 5% 5% 29%	8140

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	73% 2 8% 13% 3	2779
	11th to 20th	Day	69% 3 6% 18% 4	3048
	21st to end	Day	65% 4 14% 13% 3	3986
February	1st to 10th	Day	60% 5% 12% 16% 7% 1	1600
	11th to 20th	Day	53% 5% 13% 20% 9%	1611
	21st to end	Day	56% 4 11% 20% 9%	1650
March	1st to 10th	Day	57% 3 13% 18% 8% 1	4500
	11th to 20th	Day	55% 4 12% 17% 12%	4733
	21st to end	Day	43% 3 9% 24% 19% 1	5824
April	1st to 10th	Day	45% 3 13% 24% 14% 1	2410
	11th to 20th	Day	51% 3 10% 22% 14% 1	2572
	21st to end	Day	45% 4 12% 26% 13%	2700
May	1st to 10th	Day	47% 2 9% 27% 14% 1	6472
	11th to 20th	Day	51% 3 14% 24% 7% 1	6759
	21st to end	Day	42% 2 9% 20% 24% 2	7428
June	1st to 10th	Day	53% 4 11% 19% 13% 1	3176
	11th to 20th	Day	51% 5% 12% 22% 9% 1	3200
	21st to end	Day	48% 4 14% 26% 8% 1	3200
July	1st to 10th	Day	34% 4 18% 36% 7%	7161
	11th to 20th	Day	32% 4 16% 42% 6%	7032
	21st to end	Day	36% 4 23% 29% 9%	7092
August	1st to 10th	Day	39% 3 21% 31% 5%	4536
	11th to 20th	Day	37% 4 21% 33% 4	4508
	21st to end	Day	43% 3 23% 24% 6%	4674
September	1st to 10th	Day	45% 4 20% 23% 8% 1	2433
	11th to 20th	Day	50% 4 20% 23% 4	2280
	21st to end	Day	42% 3 17% 30% 7% 1	2200
October	1st to 10th	Day	46% 4 19% 27% 4	3349
	11th to 20th	Day	51% 3 15% 23% 8%	2922
	21st to end	Day	62% 4 16% 15% 2	3190
November	1st to 10th	Day	69% 3 11% 12% 4	1632
	11th to 20th	Day	67% 3 14% 13% 3	1470
	21st to end	Day	68% 4 12% 13% 3	1470
December	1st to 10th	Day	75% 3 11% 6% 5%	2360
	11th to 20th	Day	60% 4 15% 18% 4	2393
	21st to end	Day	55% 3 11% 20% 9% 1	3058
January	1st to 10th	Night	69% 3 11% 14% 4	7386
	11th to 20th	Night	71% 3 8% 15% 3	7056
	21st to end	Night	67% 3 12% 13% 5%	6977
February	1st to 10th	Night	59% 3 12% 17% 9% 1	2800
	11th to 20th	Night	52% 3 13% 23% 9%	2699
	21st to end	Night	50% 4 15% 22% 9%	1985
March	1st to 10th	Night	48% 3 15% 20% 12% 2	5374
	11th to 20th	Night	51% 3 9% 24% 12%	5238
	21st to end	Night	35% 4 9% 30% 22% 1	5121
April	1st to 10th	Night	44% 2 13% 23% 16% 3	1990
	11th to 20th	Night	49% 3 9% 21% 17% 2	1779
	21st to end	Night	45% 3 8% 25% 17% 2	1696
May	1st to 10th	Night	43% 3 14% 25% 15% 1	3507
	11th to 20th	Night	51% 3 13% 22% 8% 2	3161
	21st to end	Night	43% 2 10% 19% 21% 4	3470
June	1st to 10th	Night	44% 3 12% 26% 14% 1	1220
	11th to 20th	Night	47% 5% 13% 22% 12% 1	1200
	21st to end	Night	43% 6% 17% 23% 11%	1200
July	1st to 10th	Night	33% 3 21% 34% 9%	2690
	11th to 20th	Night	27% 4 17% 45% 6%	2808
	21st to end	Night	32% 4 27% 30% 6%	3456
August	1st to 10th	Night	28% 4 21% 39% 8%	2600
	11th to 20th	Night	35% 3 22% 32% 7%	2616
	21st to end	Night	38% 4 21% 31% 6%	3234
September	1st to 10th	Night	37% 4 19% 30% 10% 1	1965
	11th to 20th	Night	44% 4 16% 29% 6%	2119
	21st to end	Night	41% 3 14% 30% 11% 1	2200
October	1st to 10th	Night	41% 3 17% 32% 7%	3801
	11th to 20th	Night	47% 2 15% 27% 9%	4227
	21st to end	Night	60% 5% 13% 20% 3	4610
November	1st to 10th	Night	67% 3 12% 13% 5%	2884
	11th to 20th	Night	65% 3 15% 14% 4	3150
	21st to end	Night	67% 3 12% 14% 4	3150
December	1st to 10th	Night	77% 3 9% 9% 2	5050
	11th to 20th	Night	60% 4 14% 14% 8%	6015
	21st to end	Night	59% 2 9% 20% 9%	8140

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	15% 11% 34% 31% 9%	220
	11th to 20th	Day	12% 8% 37% 32% 10% 1	275
	21st to end	Day	22% 7% 28% 33% 9% 1	330
February	1st to 10th	Day	13% 11% 36% 28% 10% 2	300
	11th to 20th	Day	10% 8% 34% 32% 14% 2	300
	21st to end	Day	8% 16% 38% 24% 13% 2	249
March	1st to 10th	Day	14% 8% 38% 26% 12% 2	300
	11th to 20th	Day	11% 11% 34% 30% 11% 4	300
	21st to end	Day	14% 13% 30% 27% 14% 2	483
April	1st to 10th	Day	17% 11% 34% 26% 7% 4	510
	11th to 20th	Day	19% 12% 32% 23% 11% 2	690
	21st to end	Day	13% 12% 37% 24% 12% 2	700
May	1st to 10th	Day	20% 13% 31% 25% 11% 1	703
	11th to 20th	Day	17% 13% 33% 23% 12% 2	725
	21st to end	Day	23% 7% 29% 27% 11% 3	789
June	1st to 10th	Day	25% 12% 29% 21% 11% 3	730
	11th to 20th	Day	23% 12% 27% 24% 10% 5%	730
	21st to end	Day	20% 10% 25% 26% 13% 5%	730
July	1st to 10th	Day	12% 11% 30% 27% 16% 4	721
	11th to 20th	Day	15% 8% 27% 31% 14% 5%	718
	21st to end	Day	14% 8% 28% 29% 16% 6%	794
August	1st to 10th	Day	15% 9% 26% 27% 18% 5%	726
	11th to 20th	Day	15% 8% 27% 29% 16% 6%	715
	21st to end	Day	22% 7% 29% 26% 14% 2	803
September	1st to 10th	Day	21% 13% 34% 23% 8% 1	563
	11th to 20th	Day	23% 9% 32% 24% 10% 2	410
	21st to end	Day	18% 15% 31% 26% 9% 1	330
October	1st to 10th	Day	23% 12% 31% 25% 8% 2	330
	11th to 20th	Day	25% 14% 37% 13% 9% 2	330
	21st to end	Day	25% 15% 28% 24% 7% 1	363
November	1st to 10th	Day	23% 13% 30% 22% 9% 3	330
	11th to 20th	Day	22% 10% 34% 28% 5% 1	330
	21st to end	Day	15% 15% 41% 22% 6% 2	330
December	1st to 10th	Day	12% 11% 33% 28% 12% 3	330
	11th to 20th	Day	18% 13% 35% 28% 5%	245
	21st to end	Day	12% 10% 28% 33% 14% 4	242
January	1st to 10th	Night	15% 10% 31% 31% 11% 1	1050
	11th to 20th	Night	14% 9% 38% 28% 9% 1	1031
	21st to end	Night	20% 10% 33% 28% 8% 1	1100
February	1st to 10th	Night	13% 9% 35% 32% 11% 1	1000
	11th to 20th	Night	10% 7% 32% 34% 15% 3	979
	21st to end	Night	8% 9% 36% 31% 15% 1	665
March	1st to 10th	Night	13% 8% 25% 36% 17% 1	800
	11th to 20th	Night	13% 10% 33% 30% 13% 2	715
	21st to end	Night	11% 7% 30% 33% 16% 4	660
April	1st to 10th	Night	15% 7% 24% 36% 17% 2	600
	11th to 20th	Night	18% 5% 33% 30% 13% 2	593
	21st to end	Night	13% 9% 34% 35% 8% 1	600
May	1st to 10th	Night	19% 9% 30% 29% 11% 1	600
	11th to 20th	Night	18% 11% 30% 29% 12% 2	591
	21st to end	Night	22% 7% 28% 32% 11%	650
June	1st to 10th	Night	21% 6% 25% 30% 14% 2	420
	11th to 20th	Night	22% 6% 24% 36% 11% 2	400
	21st to end	Night	21% 5% 21% 39% 15% 1	400
July	1st to 10th	Night	14% 5% 26% 37% 17% 1	390
	11th to 20th	Night	11% 5% 25% 37% 19% 2	434
	21st to end	Night	12% 4 26% 35% 18% 4	657
August	1st to 10th	Night	14% 5% 26% 31% 22% 2	597
	11th to 20th	Night	15% 6% 23% 29% 24% 3	594
	21st to end	Night	20% 5% 27% 33% 14% 1	660
September	1st to 10th	Night	16% 7% 29% 29% 17% 1	600
	11th to 20th	Night	22% 6% 26% 32% 13%	600
	21st to end	Night	19% 10% 27% 34% 10% 1	600
October	1st to 10th	Night	23% 6% 30% 30% 10% 1	720
	11th to 20th	Night	22% 11% 27% 29% 9% 1	1000
	21st to end	Night	27% 12% 28% 23% 10% 1	1100
November	1st to 10th	Night	22% 10% 30% 27% 9% 1	1025
	11th to 20th	Night	21% 11% 33% 25% 8% 1	1050
	21st to end	Night	16% 14% 33% 28% 8% 1	1050
December	1st to 10th	Night	14% 11% 33% 28% 11% 3	1050
	11th to 20th	Night	18% 12% 35% 23% 10% 3	1050
	21st to end	Night	17% 7% 29% 29% 15% 3	1155

Page generated at 2026-01-14 00:14:26. Version ac07

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