Chena Hot Springs
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Chena Hot Springs clear sky chart from 2005-11-06 to 2024-11-05.

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	13% 12% 4 11% 7% 6% 6% 4 6% 7% 24%	107172
	Night	6% 12% 5% 13% 7% 6% 6% 5% 6% 7% 28%	100459
Transparency	Day	57% 8% 14% 15% 4 1	106827
	Night	54% 7% 12% 17% 9% 2	100451
Seeing	Day	17% 7% 17% 27% 24% 10%	18703
	Night	12% 5% 16% 31% 27% 8%	22893

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	2 10% 5% 11% 7% 4 4 3 4 7% 43%	856
	11th to 20th	Day	2 9% 4 12% 9% 7% 7% 3 6% 9% 32%	1258
	21st to end	Day	2 9% 5% 12% 10% 7% 4 6% 9% 6% 29%	1681
February	1st to 10th	Day	2 10% 4 12% 7% 7% 5% 4 4 6% 38%	1140
	11th to 20th	Day	2 10% 6% 13% 8% 8% 7% 7% 9% 7% 25%	1382
	21st to end	Day	2 10% 8% 14% 8% 7% 7% 7% 5% 6% 26%	1256
March	1st to 10th	Day	1 13% 8% 19% 9% 6% 6% 4 5% 3 25%	3035
	11th to 20th	Day	2 9% 6% 15% 7% 6% 6% 6% 8% 8% 27%	3278
	21st to end	Day	3 12% 5% 12% 7% 5% 6% 4 7% 8% 30%	4101
April	1st to 10th	Day	4 16% 5% 12% 7% 7% 7% 4 6% 7% 24%	2437
	11th to 20th	Day	3 11% 4 10% 6% 5% 5% 4 6% 8% 38%	2654
	21st to end	Day	4 10% 4 7% 6% 7% 6% 5% 7% 8% 37%	2874
May	1st to 10th	Day	8% 16% 6% 13% 7% 7% 6% 5% 6% 6% 19%	5240
	11th to 20th	Day	5% 11% 4 11% 7% 7% 7% 5% 7% 8% 29%	5447
	21st to end	Day	14% 10% 3 10% 7% 6% 6% 5% 7% 7% 24%	6479
June	1st to 10th	Day	13% 8% 4 10% 7% 6% 6% 5% 7% 8% 25%	3724
	11th to 20th	Day	14% 8% 3 8% 7% 6% 6% 6% 8% 8% 26%	3800
	21st to end	Day	17% 8% 3 7% 6% 6% 5% 5% 7% 8% 28%	3800
July	1st to 10th	Day	30% 13% 3 8% 4 5% 5% 4 6% 6% 16%	6313
	11th to 20th	Day	19% 9% 4 9% 6% 6% 6% 4 6% 7% 25%	5897
	21st to end	Day	24% 10% 3 8% 5% 5% 4 4 6% 7% 25%	6107
August	1st to 10th	Day	25% 11% 3 9% 6% 4 5% 4 6% 6% 20%	5144
	11th to 20th	Day	22% 15% 3 10% 7% 6% 6% 4 6% 7% 15%	4808
	21st to end	Day	22% 17% 4 10% 7% 6% 6% 5% 6% 5% 14%	4929
September	1st to 10th	Day	19% 13% 4 10% 5% 6% 5% 3 6% 7% 22%	2479
	11th to 20th	Day	21% 17% 5% 9% 6% 5% 4 4 5% 5% 20%	2226
	21st to end	Day	16% 20% 7% 10% 6% 5% 4 4 4 6% 18%	2090
October	1st to 10th	Day	8% 16% 6% 12% 5% 4 4 3 4 5% 31%	2950
	11th to 20th	Day	6% 14% 6% 16% 7% 6% 6% 4 5% 6% 24%	2791
	21st to end	Day	4 18% 6% 17% 9% 6% 5% 4 5% 6% 20%	2407
November	1st to 10th	Day	5% 15% 5% 12% 8% 7% 5% 7% 8% 6% 23%	1164
	11th to 20th	Day	5% 12% 5% 13% 9% 9% 5% 4 6% 7% 25%	950
	21st to end	Day	4 14% 5% 15% 8% 4 6% 4 5% 7% 28%	671
December	1st to 10th	Day	6% 16% 5% 11% 6% 6% 4 4 8% 10% 25%	570
	11th to 20th	Day	1 12% 5% 16% 8% 8% 10% 5% 8% 6% 21%	530
	21st to end	Day	1 10% 5% 11% 8% 8% 6% 6% 10% 10% 26%	704
January	1st to 10th	Night	2 9% 4 12% 6% 5% 4 4 6% 8% 40%	6099
	11th to 20th	Night	2 10% 5% 14% 9% 6% 5% 5% 6% 8% 30%	5682
	21st to end	Night	3 8% 4 11% 7% 6% 6% 6% 8% 8% 33%	5982
February	1st to 10th	Night	1 8% 5% 13% 7% 6% 4 4 6% 4 42%	3040
	11th to 20th	Night	2 9% 5% 12% 8% 7% 6% 5% 7% 9% 30%	2683
	21st to end	Night	3 11% 6% 17% 8% 7% 7% 5% 4 6% 26%	2198
March	1st to 10th	Night	2 12% 7% 20% 9% 7% 5% 3 3 4 28%	3818
	11th to 20th	Night	2 9% 5% 14% 8% 7% 6% 5% 7% 9% 28%	3680
	21st to end	Night	3 10% 5% 11% 6% 6% 6% 5% 7% 10% 32%	3514
April	1st to 10th	Night	3 14% 6% 11% 7% 6% 6% 5% 7% 7% 27%	1743
	11th to 20th	Night	3 10% 5% 11% 7% 5% 5% 5% 6% 8% 36%	1473
	21st to end	Night	5% 9% 3 9% 6% 6% 5% 4 7% 8% 39%	1306
May	1st to 10th	Night	8% 14% 4 12% 9% 9% 7% 5% 7% 7% 19%	1724
	11th to 20th	Night	5% 8% 3 9% 7% 6% 7% 5% 7% 11% 31%	1449
	21st to end	Night	15% 10% 3 7% 5% 5% 6% 5% 6% 8% 29%	1107
June	1st to 10th	Night	7% 9% 2 13% 8% 7% 6% 6% 5% 9% 28%	456
	11th to 20th	Night	13% 7% 4 9% 4 6% 6% 7% 8% 6% 30%	380
	21st to end	Night	14% 7% 4 6% 7% 5% 8% 4 8% 9% 28%	380
July	1st to 10th	Night	29% 12% 3 9% 6% 6% 6% 3 4 6% 17%	657
	11th to 20th	Night	19% 11% 4 9% 5% 5% 5% 3 5% 7% 28%	1071
	21st to end	Night	22% 9% 3 8% 4 4 4 4 6% 7% 28%	1453
August	1st to 10th	Night	25% 12% 3 7% 5% 4 4 4 7% 8% 21%	1791
	11th to 20th	Night	25% 14% 3 11% 6% 6% 4 3 4 5% 19%	2030
	21st to end	Night	23% 17% 4 9% 6% 5% 5% 4 5% 6% 17%	2736
September	1st to 10th	Night	18% 11% 3 9% 6% 6% 4 5% 5% 6% 27%	1701
	11th to 20th	Night	17% 15% 5% 10% 6% 5% 5% 5% 5% 6% 21%	1952
	21st to end	Night	16% 16% 5% 9% 6% 5% 7% 4 6% 5% 21%	2090
October	1st to 10th	Night	8% 16% 6% 10% 6% 5% 5% 4 4 6% 28%	4014
	11th to 20th	Night	6% 15% 6% 17% 6% 5% 5% 5% 5% 7% 23%	4135
	21st to end	Night	5% 14% 7% 19% 9% 6% 5% 3 4 5% 23%	5152
November	1st to 10th	Night	5% 17% 6% 13% 7% 6% 5% 4 4 5% 28%	3012
	11th to 20th	Night	6% 12% 7% 16% 9% 6% 5% 4 5% 6% 25%	3230
	21st to end	Night	5% 13% 4 14% 7% 6% 6% 4 6% 6% 28%	3488
December	1st to 10th	Night	6% 13% 5% 12% 7% 7% 5% 5% 6% 8% 25%	3610
	11th to 20th	Night	2 12% 7% 15% 10% 8% 8% 5% 7% 5% 20%	4660
	21st to end	Night	2 10% 5% 13% 8% 7% 7% 6% 7% 10% 26%	6963

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	42% 6% 11% 21% 13% 7%	856
	11th to 20th	Day	48% 6% 8% 21% 8% 9%	1270
	21st to end	Day	49% 5% 7% 15% 14% 9%	1681
February	1st to 10th	Day	45% 6% 6% 16% 19% 9%	1140
	11th to 20th	Day	52% 7% 10% 18% 11% 2	1389
	21st to end	Day	55% 6% 7% 19% 10% 3	1256
March	1st to 10th	Day	60% 6% 8% 11% 14% 2	3035
	11th to 20th	Day	49% 9% 10% 21% 10% 1	3278
	21st to end	Day	48% 8% 17% 17% 8% 2	4101
April	1st to 10th	Day	57% 6% 13% 15% 8% 1	2437
	11th to 20th	Day	43% 7% 17% 22% 8% 3	2654
	21st to end	Day	43% 7% 15% 26% 8%	2874
May	1st to 10th	Day	63% 8% 11% 13% 4	5240
	11th to 20th	Day	49% 9% 15% 23% 4	5450
	21st to end	Day	56% 10% 13% 17% 4	6480
June	1st to 10th	Day	54% 10% 16% 17% 3	3724
	11th to 20th	Day	52% 10% 18% 18% 1	3800
	21st to end	Day	52% 9% 22% 16% 2	3800
July	1st to 10th	Day	68% 8% 14% 8% 1	6214
	11th to 20th	Day	58% 8% 15% 19% 1	5792
	21st to end	Day	58% 8% 17% 14% 3	5914
August	1st to 10th	Day	63% 8% 18% 9% 1	5124
	11th to 20th	Day	67% 9% 16% 7%	4856
	21st to end	Day	70% 8% 16% 5%	4928
September	1st to 10th	Day	61% 9% 19% 11% 1	2479
	11th to 20th	Day	65% 8% 15% 11%	2226
	21st to end	Day	66% 8% 11% 13% 2	2090
October	1st to 10th	Day	56% 5% 10% 20% 9%	2950
	11th to 20th	Day	60% 6% 11% 20% 2	2791
	21st to end	Day	65% 5% 13% 14% 3	2407
November	1st to 10th	Day	55% 9% 14% 15% 4 2	1164
	11th to 20th	Day	56% 7% 15% 14% 8%	950
	21st to end	Day	54% 7% 11% 16% 11% 1	671
December	1st to 10th	Day	51% 9% 12% 18% 9% 2	570
	11th to 20th	Day	57% 8% 9% 18% 6% 1	532
	21st to end	Day	46% 9% 11% 19% 15% 1	704
January	1st to 10th	Night	43% 5% 12% 26% 10% 4	6099
	11th to 20th	Night	49% 7% 10% 19% 8% 6%	5732
	21st to end	Night	45% 6% 7% 13% 22% 7%	5982
February	1st to 10th	Night	42% 5% 7% 16% 22% 8%	3040
	11th to 20th	Night	48% 6% 11% 20% 12% 2	2687
	21st to end	Night	58% 5% 9% 14% 11% 3	2198
March	1st to 10th	Night	61% 4 5% 15% 14% 2	3818
	11th to 20th	Night	47% 9% 10% 22% 12% 2	3682
	21st to end	Night	43% 8% 18% 18% 10% 3	3514
April	1st to 10th	Night	51% 8% 14% 19% 7% 1	1743
	11th to 20th	Night	45% 7% 18% 21% 8% 2	1473
	21st to end	Night	41% 8% 17% 25% 9%	1306
May	1st to 10th	Night	62% 9% 13% 14% 3	1724
	11th to 20th	Night	44% 8% 13% 30% 4	1449
	21st to end	Night	49% 10% 13% 21% 7%	1107
June	1st to 10th	Night	49% 9% 19% 19% 4	456
	11th to 20th	Night	47% 12% 20% 19% 2	380
	21st to end	Night	46% 14% 22% 16% 1	380
July	1st to 10th	Night	70% 6% 14% 8% 2	647
	11th to 20th	Night	57% 7% 15% 20% 1	1053
	21st to end	Night	54% 10% 19% 13% 4	1407
August	1st to 10th	Night	60% 7% 21% 8% 3	1786
	11th to 20th	Night	68% 8% 17% 7%	2048
	21st to end	Night	66% 8% 15% 10%	2736
September	1st to 10th	Night	55% 8% 22% 13% 2	1701
	11th to 20th	Night	63% 7% 16% 13% 1	1952
	21st to end	Night	63% 8% 12% 15% 3	2090
October	1st to 10th	Night	57% 6% 9% 23% 5%	4014
	11th to 20th	Night	59% 7% 15% 16% 3	4135
	21st to end	Night	64% 5% 10% 19% 2	5152
November	1st to 10th	Night	57% 7% 13% 17% 4 2	3012
	11th to 20th	Night	59% 6% 13% 16% 4	3230
	21st to end	Night	55% 6% 11% 18% 9% 1	3488
December	1st to 10th	Night	54% 8% 12% 16% 9% 2	3610
	11th to 20th	Night	61% 8% 9% 14% 8%	4657
	21st to end	Night	49% 8% 11% 14% 16% 3	6963

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	4 11% 27% 31% 22% 4	90
	11th to 20th	Day	8% 3 21% 33% 28% 7%	90
	21st to end	Day	8% 9% 16% 29% 24% 14%	160
February	1st to 10th	Day	5% 8% 14% 33% 28% 13%	280
	11th to 20th	Day	7% 8% 19% 32% 25% 9%	349
	21st to end	Day	7% 8% 22% 32% 23% 7%	307
March	1st to 10th	Day	6% 4 18% 36% 28% 9%	370
	11th to 20th	Day	6% 8% 25% 35% 15% 10%	370
	21st to end	Day	8% 10% 22% 29% 25% 7%	578
April	1st to 10th	Day	9% 9% 23% 31% 22% 6%	635
	11th to 20th	Day	7% 8% 23% 30% 25% 7%	640
	21st to end	Day	7% 6% 19% 28% 30% 10%	650
May	1st to 10th	Day	13% 7% 21% 24% 25% 9%	653
	11th to 20th	Day	8% 8% 22% 30% 24% 8%	740
	21st to end	Day	19% 6% 15% 29% 23% 8%	1097
June	1st to 10th	Day	13% 5% 15% 28% 26% 12%	1060
	11th to 20th	Day	15% 5% 13% 25% 28% 12%	1060
	21st to end	Day	16% 3 13% 25% 29% 13%	1060
July	1st to 10th	Day	22% 4 13% 23% 27% 10%	1041
	11th to 20th	Day	24% 4 16% 23% 22% 10%	965
	21st to end	Day	22% 5% 13% 24% 22% 14%	908
August	1st to 10th	Day	29% 7% 15% 23% 19% 7%	676
	11th to 20th	Day	32% 8% 17% 22% 16% 6%	665
	21st to end	Day	31% 6% 15% 27% 16% 5%	748
September	1st to 10th	Day	27% 6% 15% 20% 21% 11%	680
	11th to 20th	Day	26% 9% 17% 23% 20% 5%	521
	21st to end	Day	28% 8% 17% 21% 16% 10%	390
October	1st to 10th	Day	19% 11% 19% 22% 17% 12%	390
	11th to 20th	Day	15% 6% 18% 23% 26% 12%	390
	21st to end	Day	12% 9% 13% 25% 24% 17%	429
November	1st to 10th	Day	12% 8% 13% 29% 27% 10%	252
	11th to 20th	Day	10% 7% 9% 27% 26% 22%	90
	21st to end	Day	11% 3 14% 32% 29% 10%	90
December	1st to 10th	Day	11% 7% 20% 37% 23% 2	90
	11th to 20th	Day	7% 8% 28% 22% 30% 6%	90
	21st to end	Day	9% 11% 18% 34% 24% 3	99
January	1st to 10th	Night	6% 5% 20% 33% 27% 9%	1130
	11th to 20th	Night	8% 5% 18% 40% 21% 7%	959
	21st to end	Night	6% 6% 22% 35% 24% 7%	980
February	1st to 10th	Night	5% 7% 19% 32% 26% 11%	850
	11th to 20th	Night	6% 7% 20% 37% 25% 5%	834
	21st to end	Night	8% 6% 20% 37% 23% 5%	703
March	1st to 10th	Night	6% 4 20% 37% 29% 4	713
	11th to 20th	Night	5% 4 21% 41% 22% 6%	628
	21st to end	Night	8% 4 17% 35% 26% 9%	627
April	1st to 10th	Night	9% 6% 14% 35% 28% 7%	570
	11th to 20th	Night	7% 3 16% 36% 29% 9%	563
	21st to end	Night	10% 2 11% 31% 36% 10%	546
May	1st to 10th	Night	11% 4 11% 28% 37% 9%	282
	11th to 20th	Night	11% 2 10% 37% 36% 4	187
	21st to end	Night	17% 4 9% 30% 34% 5%	206
June	1st to 10th	Night	12% 3 13% 27% 34% 11%	190
	11th to 20th	Night	16% 2 8% 26% 38% 10%	190
	21st to end	Night	17% 3 5% 21% 45% 10%	190
July	1st to 10th	Night	19% 2 5% 24% 42% 8%	185
	11th to 20th	Night	26% 3 11% 18% 32% 10%	184
	21st to end	Night	20% 1 10% 24% 37% 8%	208
August	1st to 10th	Night	31% 5% 10% 18% 29% 8%	314
	11th to 20th	Night	30% 5% 10% 22% 27% 6%	471
	21st to end	Night	29% 5% 6% 23% 25% 12%	627
September	1st to 10th	Night	24% 5% 8% 23% 27% 12%	570
	11th to 20th	Night	26% 5% 10% 24% 30% 5%	570
	21st to end	Night	24% 5% 15% 24% 26% 7%	570
October	1st to 10th	Night	22% 6% 17% 24% 25% 6%	798
	11th to 20th	Night	15% 6% 16% 25% 29% 9%	860
	21st to end	Night	11% 4 14% 33% 28% 10%	946
November	1st to 10th	Night	14% 6% 18% 30% 26% 6%	854
	11th to 20th	Night	12% 5% 14% 29% 28% 12%	850
	21st to end	Night	11% 4 16% 33% 26% 10%	1035
December	1st to 10th	Night	12% 7% 18% 36% 22% 6%	1130
	11th to 20th	Night	9% 5% 19% 28% 30% 9%	1130
	21st to end	Night	8% 7% 17% 32% 26% 10%	1243

Page generated at 2024-11-02 22:11:20. Version ac07

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