Medicine Lake Viewpoint
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Medicine Lake Viewpoint clear sky chart from 2005-11-06 to 2026-03-03.

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% 17% 6% 13% 6% 5% 5% 4 5% 6% 23%	134602
	Night	6% 16% 7% 14% 7% 6% 5% 4 6% 7% 23%	135269
Transparency	Day	59% 8% 12% 14% 6% 1	134303
	Night	57% 9% 14% 14% 6% 1	135148
Seeing	Day	24% 18% 29% 19% 8% 2	17714
	Night	15% 16% 35% 24% 9% 1	26224

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	1 14% 10% 24% 9% 7% 7% 5% 6% 6% 11%	3527
	11th to 20th	Day	3 15% 5% 15% 5% 5% 5% 5% 5% 6% 32%	4153
	21st to end	Day	3 21% 8% 14% 7% 5% 5% 3 5% 7% 21%	5186
February	1st to 10th	Day	3 15% 8% 16% 8% 7% 5% 4 7% 7% 20%	1680
	11th to 20th	Day	2 15% 9% 20% 7% 7% 6% 4 5% 6% 19%	1723
	21st to end	Day	2 14% 9% 19% 11% 6% 4 5% 7% 6% 17%	1723
March	1st to 10th	Day	1 15% 7% 20% 9% 8% 6% 5% 6% 6% 18%	4539
	11th to 20th	Day	2 17% 9% 18% 6% 5% 4 4 5% 6% 23%	4643
	21st to end	Day	4 23% 9% 19% 8% 5% 5% 4 5% 5% 15%	5969
April	1st to 10th	Day	4 23% 10% 17% 8% 6% 5% 4 4 5% 13%	2400
	11th to 20th	Day	5% 21% 9% 15% 8% 7% 5% 4 4 6% 17%	2514
	21st to end	Day	8% 24% 7% 13% 6% 5% 5% 4 5% 6% 17%	2742
May	1st to 10th	Day	8% 21% 6% 10% 6% 5% 5% 3 4 6% 26%	6320
	11th to 20th	Day	12% 22% 6% 13% 7% 6% 6% 4 6% 6% 14%	6594
	21st to end	Day	13% 21% 5% 10% 5% 5% 4 3 5% 6% 22%	7405
June	1st to 10th	Day	21% 16% 4 10% 6% 6% 5% 4 6% 5% 17%	3195
	11th to 20th	Day	24% 19% 4 12% 7% 5% 5% 4 4 5% 12%	3200
	21st to end	Day	19% 13% 5% 11% 8% 5% 5% 3 5% 6% 20%	3200
July	1st to 10th	Day	13% 11% 3 8% 5% 4 5% 4 5% 7% 35%	7240
	11th to 20th	Day	16% 9% 3 8% 5% 5% 5% 4 5% 6% 34%	7176
	21st to end	Day	15% 13% 4 9% 5% 5% 5% 4 6% 5% 28%	6965
August	1st to 10th	Day	15% 8% 3 8% 6% 6% 6% 5% 6% 6% 32%	4541
	11th to 20th	Day	15% 10% 4 9% 6% 6% 6% 4 6% 7% 28%	4470
	21st to end	Day	18% 11% 4 9% 5% 5% 4 3 5% 6% 29%	4610
September	1st to 10th	Day	16% 12% 4 9% 5% 5% 4 3 4 6% 33%	2400
	11th to 20th	Day	13% 15% 3 7% 5% 6% 4 3 5% 6% 33%	2327
	21st to end	Day	16% 16% 4 10% 6% 5% 4 3 3 6% 27%	2200
October	1st to 10th	Day	12% 24% 5% 10% 5% 4 4 4 6% 6% 20%	3350
	11th to 20th	Day	12% 23% 8% 9% 5% 4 5% 3 5% 7% 20%	2977
	21st to end	Day	4 19% 11% 11% 6% 5% 5% 3 4 5% 27%	3200
November	1st to 10th	Day	6% 21% 6% 13% 8% 6% 5% 4 6% 6% 18%	1710
	11th to 20th	Day	2 16% 7% 13% 6% 6% 6% 7% 6% 7% 25%	1470
	21st to end	Day	3 17% 7% 12% 10% 7% 6% 4 6% 7% 21%	1470
December	1st to 10th	Day	3 18% 8% 19% 8% 5% 4 5% 6% 7% 18%	2360
	11th to 20th	Day	2 16% 9% 16% 6% 6% 6% 5% 5% 8% 20%	2365
	21st to end	Day	1 17% 8% 17% 7% 5% 5% 3 5% 7% 24%	3058
January	1st to 10th	Night	1 14% 10% 25% 11% 7% 6% 4 5% 6% 10%	9366
	11th to 20th	Night	2 14% 7% 13% 6% 5% 5% 5% 6% 7% 29%	8801
	21st to end	Night	3 21% 7% 14% 8% 6% 5% 3 4 6% 21%	8994
February	1st to 10th	Night	4 18% 6% 16% 9% 7% 6% 4 6% 5% 18%	2940
	11th to 20th	Night	2 14% 8% 16% 8% 7% 6% 4 7% 6% 20%	2781
	21st to end	Night	2 15% 8% 13% 10% 7% 5% 4 6% 7% 22%	2082
March	1st to 10th	Night	2 13% 7% 17% 9% 7% 7% 5% 6% 7% 20%	5400
	11th to 20th	Night	2 14% 10% 19% 7% 6% 6% 5% 6% 6% 20%	5341
	21st to end	Night	5% 19% 8% 16% 8% 6% 5% 4 6% 5% 18%	5006
April	1st to 10th	Night	2 20% 9% 16% 8% 6% 5% 4 6% 7% 17%	2000
	11th to 20th	Night	4 15% 8% 13% 6% 6% 6% 4 6% 7% 25%	1836
	21st to end	Night	8% 17% 4 11% 7% 6% 5% 4 5% 7% 26%	1655
May	1st to 10th	Night	6% 17% 5% 10% 5% 4 5% 3 7% 8% 30%	3640
	11th to 20th	Night	11% 19% 5% 12% 6% 6% 5% 4 5% 7% 19%	3297
	21st to end	Night	11% 20% 4 7% 5% 4 4 4 5% 7% 29%	3470
June	1st to 10th	Night	16% 14% 3 9% 5% 5% 4 4 6% 7% 27%	1201
	11th to 20th	Night	18% 13% 4 10% 7% 6% 6% 4 6% 7% 18%	1200
	21st to end	Night	13% 10% 4 8% 6% 6% 5% 6% 6% 7% 29%	1200
July	1st to 10th	Night	15% 7% 2 5% 4 3 4 3 5% 8% 44%	2720
	11th to 20th	Night	17% 8% 2 6% 5% 5% 4 4 5% 6% 39%	2784
	21st to end	Night	17% 9% 2 7% 4 4 4 4 5% 8% 36%	3875
August	1st to 10th	Night	15% 10% 2 7% 5% 4 4 4 6% 8% 36%	2609
	11th to 20th	Night	15% 8% 3 7% 5% 5% 6% 5% 6% 9% 31%	2577
	21st to end	Night	15% 11% 3 8% 5% 5% 5% 3 6% 6% 34%	3298
September	1st to 10th	Night	14% 9% 4 8% 4 5% 4 4 6% 7% 38%	2000
	11th to 20th	Night	13% 12% 3 9% 4 4 4 3 5% 6% 37%	2072
	21st to end	Night	12% 14% 3 7% 4 5% 5% 4 6% 7% 32%	2200
October	1st to 10th	Night	8% 26% 6% 10% 6% 4 5% 3 6% 6% 21%	3846
	11th to 20th	Night	10% 16% 6% 10% 6% 5% 6% 4 7% 7% 23%	4171
	21st to end	Night	5% 20% 10% 12% 6% 5% 4 4 5% 5% 24%	4600
November	1st to 10th	Night	7% 19% 8% 12% 8% 6% 6% 5% 6% 6% 17%	2786
	11th to 20th	Night	3 17% 6% 13% 8% 7% 7% 5% 7% 8% 20%	3146
	21st to end	Night	2 17% 7% 15% 9% 7% 6% 5% 6% 7% 19%	3150
December	1st to 10th	Night	3 19% 9% 17% 7% 5% 5% 4 6% 7% 18%	5040
	11th to 20th	Night	2 17% 9% 17% 9% 7% 7% 5% 7% 7% 13%	6045
	21st to end	Night	1 15% 9% 18% 7% 5% 5% 4 6% 7% 21%	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	68% 8% 11% 9% 3 1	3527
	11th to 20th	Day	51% 6% 11% 18% 10% 4	4175
	21st to end	Day	59% 10% 16% 10% 4	5187
February	1st to 10th	Day	61% 7% 10% 9% 10% 2	1680
	11th to 20th	Day	63% 8% 9% 13% 6% 1	1731
	21st to end	Day	64% 8% 10% 11% 5% 1	1723
March	1st to 10th	Day	58% 12% 10% 10% 9%	4539
	11th to 20th	Day	60% 8% 10% 17% 5%	4643
	21st to end	Day	68% 8% 8% 10% 6% 1	5969
April	1st to 10th	Day	72% 9% 10% 7% 2	2400
	11th to 20th	Day	66% 9% 12% 11% 2	2514
	21st to end	Day	66% 10% 10% 11% 2	2742
May	1st to 10th	Day	57% 6% 15% 17% 5%	6320
	11th to 20th	Day	65% 9% 11% 11% 3	6598
	21st to end	Day	59% 9% 16% 14% 3	7406
June	1st to 10th	Day	66% 9% 9% 11% 5% 1	3195
	11th to 20th	Day	73% 9% 8% 8% 3	3200
	21st to end	Day	64% 9% 11% 11% 4 1	3200
July	1st to 10th	Day	46% 7% 9% 19% 14% 4	7161
	11th to 20th	Day	49% 7% 9% 21% 13% 1	7089
	21st to end	Day	56% 5% 12% 16% 8% 2	6770
August	1st to 10th	Day	49% 9% 10% 26% 7%	4524
	11th to 20th	Day	54% 8% 14% 19% 5%	4512
	21st to end	Day	56% 6% 12% 21% 6% 1	4609
September	1st to 10th	Day	52% 7% 14% 21% 6% 1	2400
	11th to 20th	Day	51% 8% 14% 18% 9%	2327
	21st to end	Day	58% 8% 13% 13% 6% 1	2200
October	1st to 10th	Day	62% 7% 15% 13% 3	3350
	11th to 20th	Day	64% 6% 14% 14% 1	2977
	21st to end	Day	59% 7% 18% 13% 3	3200
November	1st to 10th	Day	64% 10% 12% 10% 4 1	1710
	11th to 20th	Day	56% 12% 15% 11% 6% 1	1470
	21st to end	Day	58% 12% 14% 8% 5% 3	1470
December	1st to 10th	Day	66% 8% 14% 8% 4 1	2360
	11th to 20th	Day	62% 7% 16% 11% 4 1	2367
	21st to end	Day	53% 12% 12% 15% 8%	3058
January	1st to 10th	Night	69% 9% 10% 8% 3 1	9367
	11th to 20th	Night	52% 6% 11% 14% 14% 3	8841
	21st to end	Night	60% 9% 13% 12% 5%	8994
February	1st to 10th	Night	64% 7% 10% 9% 7% 2	2940
	11th to 20th	Night	60% 10% 12% 11% 7% 1	2783
	21st to end	Night	57% 7% 12% 15% 7% 2	2082
March	1st to 10th	Night	54% 12% 12% 14% 7% 1	5400
	11th to 20th	Night	58% 9% 14% 15% 4	5342
	21st to end	Night	61% 11% 9% 11% 7%	5006
April	1st to 10th	Night	62% 12% 13% 11% 2	2000
	11th to 20th	Night	55% 11% 15% 14% 5%	1836
	21st to end	Night	54% 12% 12% 17% 4	1655
May	1st to 10th	Night	50% 8% 18% 20% 3	3637
	11th to 20th	Night	59% 10% 11% 14% 5%	3297
	21st to end	Night	50% 12% 19% 16% 3	3470
June	1st to 10th	Night	54% 9% 14% 14% 7% 1	1201
	11th to 20th	Night	63% 10% 13% 12% 3	1200
	21st to end	Night	49% 13% 17% 16% 5% 1	1200
July	1st to 10th	Night	38% 6% 16% 22% 17% 2	2690
	11th to 20th	Night	46% 5% 12% 22% 15%	2748
	21st to end	Night	45% 5% 18% 22% 6% 3	3766
August	1st to 10th	Night	44% 9% 14% 30% 3	2601
	11th to 20th	Night	47% 9% 19% 20% 4	2601
	21st to end	Night	49% 7% 20% 18% 5%	3298
September	1st to 10th	Night	43% 9% 19% 22% 7% 1	2000
	11th to 20th	Night	46% 8% 17% 20% 8%	2072
	21st to end	Night	48% 12% 17% 16% 6% 1	2200
October	1st to 10th	Night	62% 7% 16% 12% 2	3846
	11th to 20th	Night	58% 7% 17% 15% 3	4171
	21st to end	Night	61% 7% 19% 10% 3	4600
November	1st to 10th	Night	64% 10% 13% 9% 3 1	2786
	11th to 20th	Night	59% 12% 14% 9% 6% 1	3146
	21st to end	Night	60% 10% 12% 11% 5% 2	3150
December	1st to 10th	Night	65% 7% 14% 9% 5%	5040
	11th to 20th	Night	65% 9% 13% 9% 4	6042
	21st to end	Night	57% 9% 15% 13% 6% 1	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% 20% 33% 24% 6% 2	220
	11th to 20th	Day	17% 19% 35% 23% 4 2	220
	21st to end	Day	21% 20% 37% 15% 6% 2	242
February	1st to 10th	Day	20% 21% 34% 18% 4 2	220
	11th to 20th	Day	14% 20% 35% 21% 9% 2	303
	21st to end	Day	22% 23% 34% 14% 7% 1	443
March	1st to 10th	Day	21% 24% 30% 14% 9% 1	509
	11th to 20th	Day	19% 26% 31% 16% 6% 2	500
	21st to end	Day	22% 23% 28% 18% 7% 3	550
April	1st to 10th	Day	25% 20% 32% 17% 5% 1	500
	11th to 20th	Day	20% 21% 30% 20% 8% 1	492
	21st to end	Day	21% 23% 27% 18% 8% 2	500
May	1st to 10th	Day	24% 17% 32% 18% 7% 1	503
	11th to 20th	Day	17% 14% 26% 28% 13% 2	663
	21st to end	Day	23% 13% 24% 23% 15% 2	789
June	1st to 10th	Day	28% 17% 30% 18% 6% 1	925
	11th to 20th	Day	32% 14% 28% 18% 8% 1	930
	21st to end	Day	25% 12% 26% 23% 12% 2	930
July	1st to 10th	Day	24% 13% 28% 22% 12% 1	916
	11th to 20th	Day	23% 13% 28% 25% 9% 2	887
	21st to end	Day	21% 15% 26% 21% 14% 3	614
August	1st to 10th	Day	19% 11% 30% 24% 12% 3	527
	11th to 20th	Day	22% 20% 33% 15% 9% 1	517
	21st to end	Day	23% 15% 32% 18% 9% 3	583
September	1st to 10th	Day	26% 16% 28% 19% 9% 2	530
	11th to 20th	Day	22% 19% 27% 24% 7% 2	530
	21st to end	Day	36% 24% 20% 15% 3 1	530
October	1st to 10th	Day	32% 19% 25% 15% 7% 2	530
	11th to 20th	Day	29% 22% 25% 16% 6% 1	362
	21st to end	Day	26% 21% 30% 17% 5% 1	363
November	1st to 10th	Day	33% 22% 29% 9% 4 2	264
	11th to 20th	Day	25% 20% 32% 17% 4 1	220
	21st to end	Day	20% 21% 27% 21% 8% 3	220
December	1st to 10th	Day	18% 23% 30% 18% 7% 4	220
	11th to 20th	Day	17% 20% 39% 19% 4 1	220
	21st to end	Day	14% 16% 37% 22% 7% 4	242
January	1st to 10th	Night	15% 20% 42% 18% 4 1	1160
	11th to 20th	Night	13% 19% 44% 18% 5% 1	1003
	21st to end	Night	14% 23% 40% 17% 5% 1	924
February	1st to 10th	Night	14% 20% 34% 24% 7% 1	840
	11th to 20th	Night	10% 16% 42% 25% 7%	824
	21st to end	Night	14% 15% 35% 25% 9% 1	692
March	1st to 10th	Night	10% 16% 41% 22% 9% 1	808
	11th to 20th	Night	9% 21% 41% 22% 7% 1	800
	21st to end	Night	11% 15% 32% 29% 11% 2	880
April	1st to 10th	Night	11% 17% 30% 31% 9% 1	800
	11th to 20th	Night	9% 15% 37% 26% 12% 1	648
	21st to end	Night	16% 13% 29% 32% 9% 1	455
May	1st to 10th	Night	17% 8% 23% 41% 11% 1	400
	11th to 20th	Night	12% 7% 24% 35% 20% 2	394
	21st to end	Night	19% 11% 23% 26% 20% 1	433
June	1st to 10th	Night	22% 7% 31% 25% 14% 1	400
	11th to 20th	Night	23% 9% 29% 27% 12% 1	400
	21st to end	Night	16% 9% 28% 29% 18% 1	400
July	1st to 10th	Night	21% 5% 19% 38% 16%	390
	11th to 20th	Night	19% 10% 22% 32% 17%	388
	21st to end	Night	14% 8% 19% 39% 20%	438
August	1st to 10th	Night	16% 4 17% 37% 24% 2	398
	11th to 20th	Night	16% 8% 21% 36% 18% 1	396
	21st to end	Night	19% 9% 27% 33% 13%	687
September	1st to 10th	Night	19% 11% 26% 28% 16% 1	800
	11th to 20th	Night	17% 9% 26% 30% 17% 1	800
	21st to end	Night	25% 15% 28% 22% 9% 1	800
October	1st to 10th	Night	22% 12% 32% 24% 9% 1	800
	11th to 20th	Night	18% 17% 34% 25% 6% 1	800
	21st to end	Night	18% 17% 40% 20% 4 1	880
November	1st to 10th	Night	20% 20% 39% 15% 5%	820
	11th to 20th	Night	15% 23% 43% 15% 4 1	1046
	21st to end	Night	14% 19% 43% 19% 4 1	1050
December	1st to 10th	Night	13% 22% 39% 19% 6% 1	1050
	11th to 20th	Night	13% 19% 44% 18% 5%	1144
	21st to end	Night	10% 18% 45% 19% 7% 1	1276

Page generated at 2026-02-27 23:40:23. Version ac07

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