Haines
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Haines clear sky chart from 2005-11-06 to 2025-07-06.

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	20% 20% 5% 11% 5% 5% 4 3 4 5% 18%	123457
	Night	16% 23% 6% 12% 6% 4 4 3 4 5% 18%	123919
Transparency	Day	68% 7% 10% 10% 4	123164
	Night	69% 7% 8% 10% 5% 1	123857
Seeing	Day	32% 10% 18% 20% 15% 4	17880
	Night	35% 12% 20% 20% 12% 2	24146

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% 20% 7% 16% 8% 6% 4 2 3 5% 23%	2440
	11th to 20th	Day	8% 25% 5% 11% 7% 5% 4 3 3 5% 24%	2702
	21st to end	Day	8% 28% 8% 18% 8% 5% 5% 3 4 4 9%	3194
February	1st to 10th	Day	8% 23% 6% 10% 6% 4 4 3 5% 5% 25%	1450
	11th to 20th	Day	10% 28% 6% 12% 5% 4 4 2 4 5% 19%	1577
	21st to end	Day	7% 26% 5% 9% 4 3 2 3 6% 6% 28%	1485
March	1st to 10th	Day	3 23% 6% 12% 6% 8% 7% 4 6% 5% 19%	4445
	11th to 20th	Day	4 24% 6% 13% 6% 5% 5% 3 4 5% 24%	4752
	21st to end	Day	4 19% 5% 10% 6% 5% 5% 4 5% 8% 30%	5877
April	1st to 10th	Day	8% 31% 7% 11% 7% 6% 4 3 3 4 16%	2403
	11th to 20th	Day	9% 24% 5% 10% 7% 5% 5% 3 5% 6% 22%	2736
	21st to end	Day	16% 26% 4 10% 5% 5% 5% 3 5% 5% 17%	2800
May	1st to 10th	Day	14% 22% 7% 12% 6% 6% 5% 3 4 5% 15%	6842
	11th to 20th	Day	9% 21% 7% 14% 6% 6% 6% 4 5% 6% 18%	7193
	21st to end	Day	15% 15% 6% 14% 7% 6% 5% 4 5% 6% 17%	7907
June	1st to 10th	Day	25% 16% 5% 10% 6% 5% 5% 3 6% 5% 15%	3419
	11th to 20th	Day	28% 15% 4 10% 5% 4 3 3 5% 6% 18%	3600
	21st to end	Day	30% 13% 3 8% 5% 4 5% 4 5% 6% 16%	3600
July	1st to 10th	Day	24% 12% 4 9% 6% 5% 5% 4 5% 5% 20%	5482
	11th to 20th	Day	44% 18% 3 7% 3 2 2 2 4 4 10%	5124
	21st to end	Day	39% 21% 4 6% 3 2 3 2 3 3 14%	5486
August	1st to 10th	Day	25% 9% 3 7% 3 3 3 3 4 5% 36%	4810
	11th to 20th	Day	35% 13% 3 7% 3 3 3 2 3 3 26%	4340
	21st to end	Day	42% 19% 4 8% 3 3 2 2 2 3 12%	4825
September	1st to 10th	Day	50% 12% 3 6% 3 3 3 2 3 3 12%	2294
	11th to 20th	Day	41% 14% 4 7% 4 3 2 2 4 4 16%	2280
	21st to end	Day	44% 17% 4 9% 4 3 2 2 3 2 9%	2021
October	1st to 10th	Day	25% 24% 6% 12% 6% 4 3 2 3 3 12%	3170
	11th to 20th	Day	27% 27% 5% 10% 4 3 3 3 3 3 13%	2885
	21st to end	Day	18% 22% 5% 12% 5% 5% 4 3 3 5% 17%	2768
November	1st to 10th	Day	16% 29% 7% 8% 4 3 3 3 4 6% 16%	1424
	11th to 20th	Day	16% 25% 5% 11% 5% 5% 4 3 4 6% 16%	1275
	21st to end	Day	16% 26% 9% 13% 5% 5% 3 2 4 5% 12%	1200
December	1st to 10th	Day	13% 26% 9% 14% 7% 4 4 4 4 5% 9%	1746
	11th to 20th	Day	6% 21% 6% 10% 8% 7% 5% 4 5% 8% 20%	1677
	21st to end	Day	13% 33% 8% 12% 5% 4 3 2 3 4 15%	2228
January	1st to 10th	Night	8% 21% 6% 14% 6% 5% 4 2 4 5% 26%	7502
	11th to 20th	Night	8% 22% 6% 13% 7% 4 3 2 3 4 26%	7196
	21st to end	Night	11% 26% 7% 19% 9% 6% 5% 3 3 3 7%	7770
February	1st to 10th	Night	11% 24% 5% 10% 5% 4 3 3 5% 6% 25%	2949
	11th to 20th	Night	10% 29% 7% 11% 6% 4 3 2 4 5% 18%	2707
	21st to end	Night	8% 24% 6% 9% 6% 5% 4 4 4 7% 23%	2145
March	1st to 10th	Night	3 22% 7% 17% 7% 7% 6% 3 4 4 20%	5428
	11th to 20th	Night	5% 22% 7% 14% 6% 6% 5% 4 5% 5% 20%	5213
	21st to end	Night	7% 19% 6% 12% 6% 5% 4 3 5% 7% 25%	5059
April	1st to 10th	Night	10% 28% 7% 11% 5% 5% 5% 3 5% 5% 16%	1995
	11th to 20th	Night	9% 23% 5% 11% 5% 6% 5% 3 5% 5% 22%	1613
	21st to end	Night	18% 25% 6% 11% 6% 3 4 3 5% 4 18%	1600
May	1st to 10th	Night	16% 22% 6% 13% 6% 5% 3 3 4 4 17%	3108
	11th to 20th	Night	11% 18% 8% 16% 5% 5% 4 4 6% 5% 19%	2702
	21st to end	Night	15% 16% 8% 16% 7% 5% 5% 4 5% 5% 14%	2968
June	1st to 10th	Night	28% 16% 5% 11% 5% 4 2 3 5% 5% 16%	979
	11th to 20th	Night	30% 14% 4 8% 5% 3 5% 3 5% 6% 18%	800
	21st to end	Night	31% 12% 3 10% 3 4 4 4 6% 5% 17%	800
July	1st to 10th	Night	23% 14% 5% 14% 4 4 4 3 4 6% 19%	1586
	11th to 20th	Night	38% 23% 4 9% 3 2 3 2 3 3 11%	1835
	21st to end	Night	40% 20% 4 9% 3 2 3 2 3 3 13%	2066
August	1st to 10th	Night	24% 12% 2 7% 3 2 2 2 5% 4 36%	2124
	11th to 20th	Night	32% 13% 3 8% 4 3 3 2 3 5% 23%	2498
	21st to end	Night	43% 18% 3 7% 2 2 2 2 2 4 15%	2842
September	1st to 10th	Night	46% 14% 4 7% 4 3 3 2 3 2 10%	1886
	11th to 20th	Night	37% 15% 4 8% 3 4 2 2 2 4 17%	1900
	21st to end	Night	45% 16% 4 9% 4 3 3 2 2 3 9%	2155
October	1st to 10th	Night	28% 23% 6% 14% 4 3 3 2 3 3 12%	3800
	11th to 20th	Night	25% 27% 6% 12% 5% 4 4 3 3 3 10%	4042
	21st to end	Night	18% 21% 5% 13% 6% 4 3 3 4 4 18%	4790
November	1st to 10th	Night	17% 28% 5% 11% 5% 4 3 2 4 4 16%	2874
	11th to 20th	Night	13% 27% 6% 10% 6% 4 5% 2 3 7% 17%	3123
	21st to end	Night	13% 30% 7% 13% 5% 4 3 2 4 7% 12%	3200
December	1st to 10th	Night	12% 29% 9% 13% 5% 3 3 3 4 6% 14%	5385
	11th to 20th	Night	8% 22% 5% 11% 7% 6% 5% 4 5% 6% 20%	6510
	21st to end	Night	12% 33% 8% 13% 5% 4 3 2 3 4 13%	8769

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	63% 7% 4 12% 10% 4	2440
	11th to 20th	Day	60% 10% 5% 10% 11% 4	2720
	21st to end	Day	80% 5% 4 5% 5% 1	3194
February	1st to 10th	Day	62% 6% 8% 11% 10% 3	1450
	11th to 20th	Day	70% 4 7% 6% 10% 3	1585
	21st to end	Day	58% 5% 10% 14% 11% 2	1485
March	1st to 10th	Day	62% 6% 10% 10% 11% 1	4445
	11th to 20th	Day	62% 7% 5% 11% 14%	4752
	21st to end	Day	50% 6% 13% 27% 4	5877
April	1st to 10th	Day	74% 7% 5% 9% 4	2403
	11th to 20th	Day	62% 10% 9% 11% 6% 1	2736
	21st to end	Day	70% 8% 10% 9% 3	2800
May	1st to 10th	Day	69% 8% 8% 13% 2	6842
	11th to 20th	Day	67% 7% 9% 12% 4	7196
	21st to end	Day	65% 10% 13% 10% 2	7908
June	1st to 10th	Day	70% 10% 10% 7% 2	3419
	11th to 20th	Day	68% 8% 14% 9%	3600
	21st to end	Day	69% 10% 15% 5% 1	3600
July	1st to 10th	Day	60% 10% 18% 10% 2	5398
	11th to 20th	Day	80% 7% 10% 3	5035
	21st to end	Day	75% 5% 13% 7%	5313
August	1st to 10th	Day	51% 8% 15% 20% 6%	4791
	11th to 20th	Day	64% 6% 19% 11% 1	4382
	21st to end	Day	79% 5% 9% 7%	4824
September	1st to 10th	Day	80% 6% 7% 6% 1	2294
	11th to 20th	Day	74% 6% 6% 12% 3	2280
	21st to end	Day	84% 4 5% 7% 1	2021
October	1st to 10th	Day	77% 6% 10% 6% 2	3170
	11th to 20th	Day	78% 6% 6% 9% 2	2885
	21st to end	Day	70% 8% 14% 7% 1	2768
November	1st to 10th	Day	72% 5% 6% 11% 5% 1	1424
	11th to 20th	Day	72% 6% 7% 10% 5%	1275
	21st to end	Day	76% 5% 7% 8% 5%	1200
December	1st to 10th	Day	78% 6% 7% 7% 2	1746
	11th to 20th	Day	61% 9% 11% 9% 9%	1678
	21st to end	Day	77% 4 5% 9% 4 1	2228
January	1st to 10th	Night	61% 6% 6% 15% 11% 1	7502
	11th to 20th	Night	60% 6% 7% 9% 9% 8%	7240
	21st to end	Night	79% 8% 4 5% 4	7770
February	1st to 10th	Night	62% 5% 8% 11% 9% 4	2949
	11th to 20th	Night	71% 4 6% 8% 9% 2	2710
	21st to end	Night	62% 5% 8% 13% 9% 3	2145
March	1st to 10th	Night	62% 6% 9% 14% 9% 1	5428
	11th to 20th	Night	66% 6% 5% 11% 12%	5215
	21st to end	Night	54% 8% 12% 20% 5%	5059
April	1st to 10th	Night	72% 6% 8% 9% 4	1995
	11th to 20th	Night	64% 8% 8% 13% 6% 1	1613
	21st to end	Night	71% 6% 8% 11% 4	1600
May	1st to 10th	Night	66% 9% 5% 17% 3	3105
	11th to 20th	Night	63% 9% 12% 11% 4	2702
	21st to end	Night	68% 9% 12% 10% 1	2968
June	1st to 10th	Night	71% 10% 9% 6% 4	979
	11th to 20th	Night	69% 11% 13% 7% 1	800
	21st to end	Night	67% 13% 15% 5%	800
July	1st to 10th	Night	66% 7% 19% 6% 2	1561
	11th to 20th	Night	80% 6% 10% 4	1802
	21st to end	Night	79% 5% 11% 5% 1	2000
August	1st to 10th	Night	51% 12% 13% 22% 3	2118
	11th to 20th	Night	62% 9% 18% 8% 3	2522
	21st to end	Night	77% 6% 9% 8%	2842
September	1st to 10th	Night	82% 7% 6% 4 1	1886
	11th to 20th	Night	75% 4 6% 12% 3	1900
	21st to end	Night	83% 5% 4 6% 2	2155
October	1st to 10th	Night	77% 7% 5% 10% 2	3800
	11th to 20th	Night	80% 5% 7% 7% 2	4042
	21st to end	Night	69% 7% 11% 11% 3	4790
November	1st to 10th	Night	73% 6% 7% 10% 5%	2874
	11th to 20th	Night	71% 7% 6% 10% 5% 1	3123
	21st to end	Night	76% 5% 6% 8% 5%	3200
December	1st to 10th	Night	73% 5% 11% 8% 4	5385
	11th to 20th	Night	64% 8% 10% 12% 6%	6508
	21st to end	Night	78% 5% 5% 8% 4 1	8769

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	17% 16% 23% 29% 12% 3	139
	11th to 20th	Day	29% 13% 29% 19% 11% 1	200
	21st to end	Day	29% 20% 17% 20% 12% 2	305
February	1st to 10th	Day	20% 14% 30% 21% 13% 2	400
	11th to 20th	Day	23% 14% 23% 23% 14% 3	395
	21st to end	Day	20% 15% 30% 21% 10% 3	331
March	1st to 10th	Day	14% 15% 26% 25% 16% 4	400
	11th to 20th	Day	20% 17% 26% 21% 15% 2	400
	21st to end	Day	17% 13% 23% 24% 18% 5%	530
April	1st to 10th	Day	21% 15% 28% 22% 12% 2	503
	11th to 20th	Day	19% 13% 21% 23% 19% 4	690
	21st to end	Day	27% 12% 22% 20% 16% 3	700
May	1st to 10th	Day	29% 12% 20% 21% 14% 3	703
	11th to 20th	Day	18% 10% 18% 25% 23% 6%	725
	21st to end	Day	21% 9% 18% 25% 22% 6%	790
June	1st to 10th	Day	30% 10% 17% 19% 18% 6%	839
	11th to 20th	Day	33% 5% 14% 24% 19% 5%	930
	21st to end	Day	32% 7% 10% 20% 23% 8%	930
July	1st to 10th	Day	30% 5% 15% 24% 22% 5%	713
	11th to 20th	Day	45% 9% 13% 16% 15% 3	668
	21st to end	Day	47% 6% 9% 17% 18% 4	739
August	1st to 10th	Day	38% 8% 11% 21% 17% 5%	676
	11th to 20th	Day	53% 8% 10% 14% 11% 4	665
	21st to end	Day	55% 8% 10% 16% 11% 1	748
September	1st to 10th	Day	48% 7% 11% 17% 15% 2	504
	11th to 20th	Day	45% 6% 14% 20% 12% 3	490
	21st to end	Day	51% 12% 16% 11% 9% 2	443
October	1st to 10th	Day	41% 13% 17% 17% 8% 4	390
	11th to 20th	Day	47% 13% 18% 13% 5% 4	390
	21st to end	Day	33% 9% 28% 18% 10% 2	429
November	1st to 10th	Day	31% 13% 31% 13% 10% 2	252
	11th to 20th	Day	34% 15% 21% 18% 10% 3	200
	21st to end	Day	29% 16% 32% 15% 9% 1	200
December	1st to 10th	Day	32% 14% 21% 20% 12% 2	200
	11th to 20th	Day	27% 10% 21% 21% 18% 3	153
	21st to end	Day	23% 13% 30% 24% 8% 3	110
January	1st to 10th	Night	30% 12% 25% 23% 9% 1	900
	11th to 20th	Night	32% 20% 25% 16% 7% 1	900
	21st to end	Night	34% 16% 21% 19% 9% 1	990
February	1st to 10th	Night	25% 13% 26% 26% 9% 2	900
	11th to 20th	Night	26% 13% 25% 24% 11% 1	884
	21st to end	Night	21% 12% 29% 27% 11% 1	743
March	1st to 10th	Night	19% 14% 27% 22% 15% 2	812
	11th to 20th	Night	23% 14% 29% 22% 10% 2	705
	21st to end	Night	22% 9% 24% 23% 19% 3	660
April	1st to 10th	Night	27% 11% 22% 22% 16% 3	600
	11th to 20th	Night	22% 10% 22% 25% 20% 1	593
	21st to end	Night	33% 11% 16% 23% 16% 3	600
May	1st to 10th	Night	39% 8% 13% 21% 15% 4	474
	11th to 20th	Night	26% 8% 16% 23% 23% 4	394
	21st to end	Night	20% 9% 15% 23% 29% 4	433
June	1st to 10th	Night	35% 11% 15% 16% 21% 3	289
	11th to 20th	Night	39% 4 13% 18% 20% 8%	200
	21st to end	Night	39% 10% 7% 15% 22% 9%	200
July	1st to 10th	Night	37% 9% 12% 18% 19% 5%	190
	11th to 20th	Night	48% 8% 9% 14% 17% 5%	332
	21st to end	Night	50% 7% 8% 15% 14% 6%	416
August	1st to 10th	Night	43% 6% 10% 16% 19% 6%	503
	11th to 20th	Night	54% 7% 9% 13% 12% 5%	564
	21st to end	Night	60% 5% 9% 13% 11% 1	627
September	1st to 10th	Night	55% 8% 11% 18% 8% 1	570
	11th to 20th	Night	47% 8% 12% 17% 14% 2	570
	21st to end	Night	55% 10% 13% 13% 7% 2	738
October	1st to 10th	Night	48% 9% 17% 17% 9% 1	760
	11th to 20th	Night	54% 11% 16% 13% 6% 1	760
	21st to end	Night	38% 12% 23% 17% 9% 1	939
November	1st to 10th	Night	35% 14% 23% 20% 8% 1	880
	11th to 20th	Night	31% 14% 25% 17% 11% 2	900
	21st to end	Night	35% 15% 22% 19% 8% 1	900
December	1st to 10th	Night	34% 13% 19% 23% 11% 1	1000
	11th to 20th	Night	29% 12% 24% 24% 9% 1	1100
	21st to end	Night	32% 14% 21% 21% 10% 2	1120

Page generated at 2025-07-02 21:30:14. Version ac07

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