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 2024-01-14.

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	12% 9% 4 8% 7% 4 6% 5% 6% 7% 32%	74632
	Night	11% 10% 5% 8% 7% 4 5% 5% 6% 7% 32%	75134
Transparency	Day	51% 4 15% 22% 8%	74304
	Night	52% 3 14% 22% 9% 1	74982
Seeing	Day	18% 10% 31% 27% 12% 3	14898
	Night	17% 8% 30% 31% 13% 2	24479

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% 15% 8% 14% 10% 4 7% 6% 9% 5% 15%	1139
	11th to 20th	Day	6% 15% 7% 10% 9% 4 7% 6% 8% 7% 21%	1206
	21st to end	Day	12% 19% 6% 9% 8% 4 7% 6% 7% 6% 16%	1580
February	1st to 10th	Day	7% 8% 4 10% 8% 5% 11% 10% 8% 8% 20%	1440
	11th to 20th	Day	6% 10% 4 8% 9% 4 10% 10% 6% 7% 25%	1439
	21st to end	Day	5% 9% 5% 11% 11% 6% 7% 6% 6% 7% 27%	1480
March	1st to 10th	Day	9% 10% 4 10% 9% 6% 6% 5% 5% 7% 28%	1800
	11th to 20th	Day	9% 9% 6% 9% 7% 4 6% 5% 7% 6% 33%	1874
	21st to end	Day	8% 8% 5% 8% 8% 4 7% 6% 6% 8% 33%	2315
April	1st to 10th	Day	9% 9% 3 7% 7% 4 5% 5% 6% 7% 39%	2168
	11th to 20th	Day	11% 12% 3 7% 6% 4 5% 4 5% 7% 36%	2312
	21st to end	Day	9% 8% 4 7% 8% 4 6% 5% 6% 7% 36%	2430
May	1st to 10th	Day	15% 10% 3 7% 6% 3 6% 5% 5% 6% 33%	2568
	11th to 20th	Day	9% 7% 3 6% 6% 4 5% 5% 6% 7% 42%	2655
	21st to end	Day	19% 7% 3 5% 5% 3 5% 4 5% 6% 37%	2918
June	1st to 10th	Day	17% 9% 3 6% 6% 4 5% 6% 5% 7% 32%	2858
	11th to 20th	Day	19% 7% 4 7% 5% 4 5% 6% 7% 7% 29%	2880
	21st to end	Day	16% 7% 3 6% 7% 3 6% 6% 6% 8% 33%	2880
July	1st to 10th	Day	10% 5% 3 6% 5% 4 5% 6% 7% 8% 41%	2880
	11th to 20th	Day	13% 5% 3 5% 5% 3 4 7% 7% 9% 39%	2837
	21st to end	Day	12% 6% 3 6% 5% 3 4 6% 7% 10% 40%	2903
August	1st to 10th	Day	10% 4 2 5% 5% 3 5% 5% 7% 8% 45%	2507
	11th to 20th	Day	12% 4 2 5% 5% 3 6% 6% 6% 9% 40%	2473
	21st to end	Day	17% 7% 3 5% 6% 3 5% 4 5% 9% 37%	2574
September	1st to 10th	Day	14% 6% 3 6% 6% 4 6% 5% 6% 8% 36%	2191
	11th to 20th	Day	17% 8% 3 6% 6% 3 5% 5% 5% 8% 34%	2052
	21st to end	Day	12% 8% 3 7% 6% 3 4 4 5% 8% 39%	1980
October	1st to 10th	Day	17% 14% 4 6% 4 3 4 4 7% 7% 29%	1854
	11th to 20th	Day	14% 16% 6% 9% 7% 4 4 5% 5% 6% 25%	1620
	21st to end	Day	18% 17% 7% 11% 7% 4 4 5% 4 5% 19%	1782
November	1st to 10th	Day	16% 19% 8% 12% 8% 4 5% 4 5% 5% 17%	1475
	11th to 20th	Day	12% 14% 4 14% 11% 4 6% 5% 4 6% 19%	1330
	21st to end	Day	8% 14% 8% 14% 11% 4 6% 6% 4 6% 19%	1330
December	1st to 10th	Day	5% 11% 7% 14% 12% 6% 9% 7% 5% 8% 16%	1330
	11th to 20th	Day	10% 16% 6% 12% 10% 5% 5% 5% 5% 5% 20%	1482
	21st to end	Day	5% 8% 3 9% 9% 5% 6% 5% 7% 7% 37%	2090
January	1st to 10th	Night	8% 14% 6% 11% 10% 5% 7% 7% 6% 6% 19%	3026
	11th to 20th	Night	8% 13% 8% 12% 10% 6% 7% 7% 7% 5% 19%	2831
	21st to end	Night	11% 15% 6% 12% 7% 4 7% 8% 5% 6% 18%	2775
February	1st to 10th	Night	6% 10% 4 9% 9% 7% 10% 7% 7% 6% 25%	2520
	11th to 20th	Night	4 9% 4 9% 10% 5% 7% 8% 6% 7% 29%	2420
	21st to end	Night	5% 8% 5% 10% 9% 3 7% 6% 5% 8% 32%	1780
March	1st to 10th	Night	10% 11% 5% 9% 7% 4 5% 5% 6% 6% 34%	2160
	11th to 20th	Night	9% 8% 5% 8% 7% 4 5% 5% 6% 8% 35%	2084
	21st to end	Night	7% 9% 4 6% 6% 4 6% 5% 6% 9% 37%	2039
April	1st to 10th	Night	9% 9% 3 7% 6% 4 4 4 6% 7% 40%	1792
	11th to 20th	Night	11% 10% 4 7% 6% 4 5% 5% 6% 6% 36%	1599
	21st to end	Night	8% 8% 4 7% 7% 4 5% 5% 5% 6% 40%	1527
May	1st to 10th	Night	17% 7% 3 6% 5% 4 5% 4 6% 7% 36%	1391
	11th to 20th	Night	10% 7% 3 5% 5% 3 5% 5% 7% 7% 42%	1241
	21st to end	Night	19% 6% 2 6% 5% 2 4 4 4 6% 42%	1358
June	1st to 10th	Night	17% 6% 2 5% 5% 3 4 5% 6% 8% 39%	1098
	11th to 20th	Night	17% 7% 3 6% 6% 4 4 5% 6% 8% 34%	1080
	21st to end	Night	14% 7% 3 6% 5% 2 6% 5% 7% 7% 37%	1080
July	1st to 10th	Night	10% 4 2 4 5% 4 4 5% 6% 8% 49%	1080
	11th to 20th	Night	10% 5% 2 4 5% 3 5% 4 7% 9% 46%	1120
	21st to end	Night	11% 5% 2 4 5% 4 4 5% 7% 8% 45%	1414
August	1st to 10th	Night	10% 3 2 3 3 2 4 5% 7% 9% 53%	1432
	11th to 20th	Night	13% 4 2 4 4 3 4 5% 6% 10% 47%	1427
	21st to end	Night	16% 6% 2 4 4 3 3 4 5% 9% 44%	1782
September	1st to 10th	Night	12% 7% 2 5% 4 4 4 5% 6% 8% 44%	1768
	11th to 20th	Night	16% 6% 2 6% 5% 3 4 4 6% 7% 39%	1907
	21st to end	Night	14% 7% 3 5% 5% 3 4 5% 5% 7% 41%	1980
October	1st to 10th	Night	16% 11% 4 6% 6% 4 4 3 3 6% 36%	2086
	11th to 20th	Night	12% 13% 5% 9% 6% 4 4 4 5% 6% 32%	2340
	21st to end	Night	17% 15% 5% 9% 7% 4 5% 4 5% 5% 24%	2574
November	1st to 10th	Night	15% 18% 7% 13% 8% 5% 4 4 4 5% 18%	2602
	11th to 20th	Night	11% 14% 6% 10% 11% 6% 5% 4 5% 6% 21%	2850
	21st to end	Night	9% 16% 7% 13% 10% 5% 5% 4 5% 5% 20%	2850
December	1st to 10th	Night	6% 13% 7% 13% 11% 6% 9% 5% 6% 6% 18%	2850
	11th to 20th	Night	9% 14% 7% 11% 10% 5% 5% 5% 5% 5% 24%	3705
	21st to end	Night	7% 9% 4 9% 9% 4 6% 5% 5% 6% 37%	5566

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	67% 3 14% 13% 3	1139
	11th to 20th	Day	60% 4 11% 21% 4	1206
	21st to end	Day	67% 4 6% 15% 7%	1580
February	1st to 10th	Day	57% 5% 13% 16% 7% 1	1440
	11th to 20th	Day	55% 6% 12% 18% 9%	1447
	21st to end	Day	56% 4 11% 21% 8%	1480
March	1st to 10th	Day	56% 4 12% 20% 7% 1	1800
	11th to 20th	Day	50% 4 13% 23% 9%	1876
	21st to end	Day	49% 4 14% 24% 8% 1	2315
April	1st to 10th	Day	45% 3 13% 24% 15% 1	2168
	11th to 20th	Day	50% 3 10% 22% 15% 1	2312
	21st to end	Day	46% 4 12% 25% 13%	2430
May	1st to 10th	Day	52% 2 8% 23% 13% 1	2568
	11th to 20th	Day	41% 3 11% 26% 16% 3	2659
	21st to end	Day	48% 3 9% 27% 13%	2918
June	1st to 10th	Day	52% 4 11% 20% 13% 1	2858
	11th to 20th	Day	52% 5% 12% 21% 9% 1	2880
	21st to end	Day	48% 4 15% 26% 7% 1	2880
July	1st to 10th	Day	38% 5% 16% 31% 11%	2801
	11th to 20th	Day	40% 4 19% 29% 7%	2750
	21st to end	Day	41% 4 22% 29% 5%	2742
August	1st to 10th	Day	36% 5% 24% 30% 6%	2491
	11th to 20th	Day	40% 5% 25% 26% 4	2473
	21st to end	Day	45% 4 25% 24% 3	2574
September	1st to 10th	Day	46% 4 20% 22% 8% 1	2191
	11th to 20th	Day	49% 4 20% 24% 4	2052
	21st to end	Day	44% 3 18% 27% 7%	1980
October	1st to 10th	Day	54% 4 15% 23% 4	1854
	11th to 20th	Day	61% 3 12% 20% 4	1620
	21st to end	Day	68% 4 10% 15% 4	1782
November	1st to 10th	Day	71% 3 12% 10% 4	1475
	11th to 20th	Day	67% 3 15% 12% 2	1330
	21st to end	Day	67% 4 14% 13% 2	1330
December	1st to 10th	Day	67% 4 15% 10% 4	1330
	11th to 20th	Day	68% 3 14% 11% 3	1483
	21st to end	Day	46% 3 13% 23% 13% 2	2090
January	1st to 10th	Night	64% 4 12% 17% 3	3026
	11th to 20th	Night	65% 3 11% 17% 4	2831
	21st to end	Night	65% 3 10% 16% 6%	2775
February	1st to 10th	Night	57% 4 12% 17% 9% 1	2520
	11th to 20th	Night	53% 4 13% 21% 9%	2422
	21st to end	Night	49% 4 14% 23% 9%	1780
March	1st to 10th	Night	50% 3 11% 25% 9% 1	2160
	11th to 20th	Night	47% 3 14% 23% 12% 1	2084
	21st to end	Night	43% 4 14% 28% 10% 1	2039
April	1st to 10th	Night	44% 2 12% 23% 16% 3	1792
	11th to 20th	Night	48% 3 9% 21% 18% 2	1599
	21st to end	Night	45% 3 8% 24% 18% 2	1527
May	1st to 10th	Night	47% 3 11% 21% 17% 2	1391
	11th to 20th	Night	40% 3 9% 27% 15% 5%	1241
	21st to end	Night	45% 3 9% 26% 16% 1	1358
June	1st to 10th	Night	44% 3 13% 25% 15% 1	1098
	11th to 20th	Night	47% 5% 13% 21% 12% 1	1080
	21st to end	Night	43% 6% 18% 23% 10%	1080
July	1st to 10th	Night	33% 4 18% 32% 13%	1050
	11th to 20th	Night	35% 4 18% 34% 9%	1084
	21st to end	Night	38% 4 22% 30% 7%	1336
August	1st to 10th	Night	26% 5% 24% 36% 8% 1	1424
	11th to 20th	Night	34% 4 24% 32% 5%	1427
	21st to end	Night	39% 3 22% 30% 6%	1782
September	1st to 10th	Night	38% 4 18% 30% 10% 1	1768
	11th to 20th	Night	44% 4 16% 30% 6%	1907
	21st to end	Night	43% 3 15% 28% 11%	1980
October	1st to 10th	Night	52% 3 13% 27% 5%	2086
	11th to 20th	Night	54% 3 14% 24% 6%	2340
	21st to end	Night	62% 4 11% 19% 4	2574
November	1st to 10th	Night	70% 3 11% 12% 4	2602
	11th to 20th	Night	65% 3 16% 14% 3	2850
	21st to end	Night	66% 3 13% 14% 3	2850
December	1st to 10th	Night	66% 4 12% 14% 4	2850
	11th to 20th	Night	62% 3 15% 13% 6%	3703
	21st to end	Night	49% 3 11% 23% 14%	5566

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	14% 11% 35% 30% 9% 1	180
	11th to 20th	Day	10% 6% 35% 35% 12% 2	214
	21st to end	Day	23% 5% 27% 34% 9% 2	264
February	1st to 10th	Day	11% 10% 38% 27% 12% 2	240
	11th to 20th	Day	11% 9% 34% 28% 15% 3	240
	21st to end	Day	6% 14% 37% 25% 16% 2	198
March	1st to 10th	Day	13% 5% 37% 29% 13% 3	240
	11th to 20th	Day	8% 10% 34% 33% 11% 4	240
	21st to end	Day	15% 13% 30% 27% 13% 2	401
April	1st to 10th	Day	17% 10% 34% 28% 8% 3	428
	11th to 20th	Day	18% 12% 31% 24% 13% 3	590
	21st to end	Day	14% 13% 36% 25% 11% 2	600
May	1st to 10th	Day	20% 12% 31% 26% 10% 1	603
	11th to 20th	Day	15% 12% 35% 24% 12% 3	625
	21st to end	Day	24% 7% 29% 26% 11% 3	679
June	1st to 10th	Day	23% 11% 29% 21% 12% 3	630
	11th to 20th	Day	23% 12% 27% 24% 10% 5%	630
	21st to end	Day	20% 9% 26% 27% 13% 4	630
July	1st to 10th	Day	12% 11% 31% 27% 16% 3	621
	11th to 20th	Day	17% 7% 27% 31% 13% 6%	618
	21st to end	Day	14% 7% 27% 29% 17% 6%	684
August	1st to 10th	Day	14% 9% 25% 27% 19% 6%	626
	11th to 20th	Day	14% 8% 26% 30% 17% 6%	615
	21st to end	Day	23% 7% 29% 26% 14% 2	693
September	1st to 10th	Day	22% 13% 34% 21% 9% 2	481
	11th to 20th	Day	22% 10% 33% 24% 10% 2	342
	21st to end	Day	19% 13% 29% 27% 11% 1	270
October	1st to 10th	Day	23% 10% 30% 27% 8% 2	270
	11th to 20th	Day	25% 13% 36% 14% 10% 2	270
	21st to end	Day	26% 12% 27% 26% 7% 1	297
November	1st to 10th	Day	24% 9% 29% 26% 10% 3	270
	11th to 20th	Day	19% 10% 36% 29% 5% 1	270
	21st to end	Day	16% 12% 40% 23% 6% 2	270
December	1st to 10th	Day	9% 10% 34% 30% 14% 3	270
	11th to 20th	Day	18% 11% 35% 30% 5%	201
	21st to end	Day	8% 9% 27% 36% 16% 4	198
January	1st to 10th	Night	15% 9% 32% 31% 11% 1	950
	11th to 20th	Night	14% 8% 37% 30% 10% 2	920
	21st to end	Night	21% 9% 32% 29% 8% 1	990
February	1st to 10th	Night	12% 9% 35% 31% 12% 1	900
	11th to 20th	Night	10% 7% 33% 32% 15% 3	879
	21st to end	Night	8% 7% 35% 32% 17% 2	596
March	1st to 10th	Night	13% 7% 25% 36% 18% 1	720
	11th to 20th	Night	13% 9% 33% 29% 14% 2	644
	21st to end	Night	12% 7% 30% 31% 16% 4	594
April	1st to 10th	Night	15% 7% 23% 36% 18% 2	540
	11th to 20th	Night	16% 5% 32% 30% 14% 3	533
	21st to end	Night	14% 9% 32% 36% 8% 1	540
May	1st to 10th	Night	20% 7% 29% 31% 11% 1	540
	11th to 20th	Night	16% 10% 30% 30% 13% 2	531
	21st to end	Night	22% 7% 29% 31% 11% 1	584
June	1st to 10th	Night	20% 6% 25% 31% 16% 3	378
	11th to 20th	Night	23% 6% 24% 35% 12% 1	360
	21st to end	Night	20% 5% 21% 39% 14% 1	360
July	1st to 10th	Night	15% 5% 26% 35% 17% 1	350
	11th to 20th	Night	13% 5% 26% 36% 19% 2	388
	21st to end	Night	13% 4 24% 36% 19% 4	591
August	1st to 10th	Night	13% 4 25% 32% 23% 2	537
	11th to 20th	Night	14% 6% 23% 29% 24% 4	534
	21st to end	Night	21% 4 26% 34% 14% 1	594
September	1st to 10th	Night	17% 6% 30% 28% 18% 1	540
	11th to 20th	Night	22% 6% 28% 32% 13%	540
	21st to end	Night	19% 9% 27% 33% 11% 1	540
October	1st to 10th	Night	25% 5% 27% 31% 11% 1	646
	11th to 20th	Night	22% 10% 27% 30% 10% 2	900
	21st to end	Night	28% 11% 26% 24% 10% 1	990
November	1st to 10th	Night	23% 9% 28% 28% 10% 2	925
	11th to 20th	Night	20% 10% 33% 27% 9% 1	950
	21st to end	Night	16% 13% 32% 28% 8% 1	950
December	1st to 10th	Night	13% 10% 33% 28% 12% 4	950
	11th to 20th	Night	18% 12% 33% 24% 11% 3	950
	21st to end	Night	17% 7% 29% 29% 15% 3	1045

Page generated at 2024-01-11 12:32:00. Version ac07

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