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 2024-12-02.

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	11% 17% 6% 12% 7% 5% 5% 4 5% 6% 23%	105903
	Night	7% 16% 6% 12% 7% 6% 5% 4 6% 7% 24%	102289
Transparency	Day	59% 9% 11% 14% 6% 1	105645
	Night	55% 10% 14% 14% 6% 1	102194
Seeing	Day	23% 18% 29% 20% 9% 2	16164
	Night	14% 16% 35% 24% 10% 1	24481

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 13% 9% 20% 9% 9% 9% 5% 7% 7% 12%	1899
	11th to 20th	Day	3 15% 6% 16% 6% 5% 4 5% 5% 6% 27%	2205
	21st to end	Day	5% 27% 8% 12% 7% 5% 5% 4 5% 6% 15%	2794
February	1st to 10th	Day	3 16% 9% 17% 8% 6% 5% 4 7% 6% 20%	1520
	11th to 20th	Day	2 15% 9% 21% 7% 7% 6% 4 5% 6% 18%	1555
	21st to end	Day	1 12% 7% 20% 11% 7% 4 5% 7% 7% 18%	1563
March	1st to 10th	Day	1 14% 6% 18% 10% 8% 6% 5% 6% 6% 19%	3138
	11th to 20th	Day	3 16% 9% 13% 6% 5% 4 4 5% 7% 27%	3237
	21st to end	Day	2 19% 8% 20% 9% 5% 5% 4 5% 6% 17%	4165
April	1st to 10th	Day	5% 23% 11% 17% 9% 6% 5% 4 4 5% 11%	2280
	11th to 20th	Day	5% 21% 9% 15% 8% 7% 5% 4 5% 6% 16%	2387
	21st to end	Day	9% 24% 7% 13% 6% 5% 5% 4 5% 6% 17%	2605
May	1st to 10th	Day	10% 23% 6% 11% 7% 5% 5% 3 4 6% 21%	4420
	11th to 20th	Day	13% 19% 5% 10% 7% 6% 6% 4 6% 6% 18%	4596
	21st to end	Day	17% 28% 6% 11% 6% 5% 4 3 4 4 12%	5161
June	1st to 10th	Day	22% 16% 4 10% 6% 6% 5% 4 6% 5% 15%	3035
	11th to 20th	Day	24% 19% 5% 12% 7% 5% 5% 4 4 4 11%	3040
	21st to end	Day	19% 13% 5% 11% 8% 5% 5% 3 5% 5% 21%	3040
July	1st to 10th	Day	15% 10% 3 8% 5% 4 4 4 4 6% 38%	5060
	11th to 20th	Day	11% 7% 3 7% 6% 5% 5% 4 5% 6% 42%	5010
	21st to end	Day	16% 13% 4 9% 5% 5% 5% 4 5% 6% 29%	4853
August	1st to 10th	Day	15% 8% 3 8% 5% 6% 6% 5% 5% 6% 33%	4401
	11th to 20th	Day	14% 10% 4 9% 6% 6% 6% 4 6% 7% 28%	4330
	21st to end	Day	18% 12% 4 10% 6% 5% 4 3 5% 6% 27%	4469
September	1st to 10th	Day	17% 12% 4 9% 5% 5% 4 3 4 5% 32%	2280
	11th to 20th	Day	14% 15% 3 7% 5% 6% 4 3 4 6% 32%	2211
	21st to end	Day	15% 17% 4 10% 6% 5% 4 3 3 6% 28%	2090
October	1st to 10th	Day	12% 24% 5% 10% 5% 4 4 4 6% 6% 20%	3248
	11th to 20th	Day	12% 23% 8% 9% 5% 4 5% 3 5% 7% 20%	2886
	21st to end	Day	4 18% 11% 12% 6% 5% 5% 3 4 5% 27%	3101
November	1st to 10th	Day	7% 20% 6% 13% 8% 6% 5% 4 6% 6% 18%	1627
	11th to 20th	Day	2 15% 7% 13% 6% 6% 6% 7% 6% 7% 25%	1400
	21st to end	Day	3 17% 7% 12% 10% 6% 6% 4 6% 7% 21%	1400
December	1st to 10th	Day	4 12% 8% 18% 10% 6% 5% 5% 4 5% 22%	1337
	11th to 20th	Day	3 17% 8% 16% 6% 6% 6% 6% 5% 7% 20%	1470
	21st to end	Day	1 20% 7% 11% 7% 6% 5% 4 5% 8% 26%	2090
January	1st to 10th	Night	2 14% 10% 21% 10% 7% 6% 5% 6% 6% 12%	5046
	11th to 20th	Night	2 14% 6% 13% 6% 6% 6% 6% 6% 8% 27%	4721
	21st to end	Night	5% 28% 8% 13% 8% 5% 5% 3 4 6% 15%	4862
February	1st to 10th	Night	4 19% 6% 17% 9% 6% 6% 4 5% 5% 18%	2660
	11th to 20th	Night	3 15% 8% 16% 8% 7% 6% 5% 6% 6% 20%	2510
	21st to end	Night	2 14% 7% 12% 10% 8% 6% 4 7% 7% 23%	1890
March	1st to 10th	Night	1 10% 7% 17% 12% 9% 9% 5% 6% 8% 16%	3736
	11th to 20th	Night	3 15% 9% 11% 6% 5% 5% 5% 8% 8% 26%	3727
	21st to end	Night	2 18% 8% 16% 8% 6% 5% 4 6% 5% 21%	3488
April	1st to 10th	Night	2 20% 9% 16% 8% 5% 6% 4 6% 7% 17%	1900
	11th to 20th	Night	4 14% 8% 13% 6% 6% 6% 4 6% 8% 25%	1743
	21st to end	Night	8% 17% 3 11% 7% 6% 5% 4 5% 7% 26%	1572
May	1st to 10th	Night	7% 21% 6% 11% 5% 4 4 4 6% 8% 24%	2540
	11th to 20th	Night	12% 19% 4 10% 5% 5% 5% 5% 5% 6% 24%	2295
	21st to end	Night	15% 26% 6% 10% 6% 5% 4 4 4 6% 16%	2414
June	1st to 10th	Night	16% 14% 3 9% 5% 5% 4 4 6% 7% 26%	1141
	11th to 20th	Night	19% 13% 4 10% 7% 6% 6% 4 6% 8% 18%	1140
	21st to end	Night	13% 9% 4 7% 5% 6% 5% 6% 6% 7% 30%	1140
July	1st to 10th	Night	14% 7% 2 6% 4 3 4 4 5% 6% 45%	1900
	11th to 20th	Night	11% 5% 2 5% 4 4 4 4 5% 7% 49%	1950
	21st to end	Night	17% 8% 2 7% 5% 4 4 4 6% 8% 36%	2696
August	1st to 10th	Night	15% 10% 2 6% 4 4 4 4 6% 8% 37%	2529
	11th to 20th	Night	14% 7% 3 7% 5% 5% 6% 5% 6% 9% 32%	2497
	21st to end	Night	15% 11% 3 8% 5% 5% 5% 3 6% 6% 32%	3197
September	1st to 10th	Night	14% 9% 4 8% 4 5% 4 4 6% 7% 36%	1900
	11th to 20th	Night	14% 13% 3 9% 4 4 4 3 5% 6% 36%	1968
	21st to end	Night	12% 13% 3 7% 4 5% 5% 4 7% 7% 31%	2090
October	1st to 10th	Night	8% 26% 6% 10% 6% 5% 5% 3 6% 6% 21%	3728
	11th to 20th	Night	10% 15% 6% 11% 6% 5% 6% 4 7% 7% 23%	4042
	21st to end	Night	5% 19% 10% 12% 6% 5% 4 4 5% 5% 24%	4457
November	1st to 10th	Night	8% 19% 8% 12% 8% 6% 6% 5% 7% 6% 16%	2650
	11th to 20th	Night	3 16% 6% 13% 8% 7% 7% 5% 7% 8% 20%	2996
	21st to end	Night	2 17% 7% 15% 9% 7% 6% 5% 6% 7% 19%	3000
December	1st to 10th	Night	4 14% 7% 17% 9% 5% 4 4 6% 7% 23%	2878
	11th to 20th	Night	3 18% 7% 15% 9% 7% 6% 5% 7% 7% 15%	3720
	21st to end	Night	1 17% 6% 12% 7% 6% 5% 5% 7% 8% 27%	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	64% 13% 12% 8% 2 1	1899
	11th to 20th	Day	55% 7% 9% 10% 12% 7%	2227
	21st to end	Day	62% 14% 13% 7% 4	2794
February	1st to 10th	Day	62% 8% 11% 9% 8% 2	1520
	11th to 20th	Day	64% 9% 8% 13% 5% 1	1563
	21st to end	Day	62% 8% 10% 12% 6% 2	1563
March	1st to 10th	Day	55% 16% 11% 9% 9%	3138
	11th to 20th	Day	54% 10% 13% 18% 5%	3237
	21st to end	Day	63% 10% 11% 9% 6% 1	4165
April	1st to 10th	Day	73% 9% 9% 7% 1	2280
	11th to 20th	Day	67% 9% 12% 10% 2	2387
	21st to end	Day	66% 10% 10% 11% 2	2605
May	1st to 10th	Day	63% 8% 13% 13% 4	4420
	11th to 20th	Day	60% 11% 13% 12% 5%	4600
	21st to end	Day	71% 10% 9% 6% 3	5162
June	1st to 10th	Day	67% 9% 9% 10% 4 1	3035
	11th to 20th	Day	73% 9% 8% 7% 2	3040
	21st to end	Day	64% 9% 10% 11% 5% 1	3040
July	1st to 10th	Day	46% 7% 8% 16% 17% 6%	4981
	11th to 20th	Day	40% 8% 9% 24% 17% 1	4923
	21st to end	Day	56% 6% 10% 15% 10% 4	4700
August	1st to 10th	Day	48% 9% 9% 27% 7%	4384
	11th to 20th	Day	53% 8% 14% 19% 5%	4372
	21st to end	Day	57% 6% 12% 21% 4	4468
September	1st to 10th	Day	54% 7% 13% 20% 5% 1	2280
	11th to 20th	Day	52% 8% 14% 17% 9%	2211
	21st to end	Day	58% 9% 12% 14% 6% 1	2090
October	1st to 10th	Day	62% 7% 15% 12% 3	3248
	11th to 20th	Day	64% 6% 14% 14% 1	2886
	21st to end	Day	59% 7% 18% 13% 3	3101
November	1st to 10th	Day	64% 10% 12% 10% 4 1	1627
	11th to 20th	Day	55% 12% 16% 11% 6% 1	1400
	21st to end	Day	58% 12% 15% 8% 5% 3	1400
December	1st to 10th	Day	62% 10% 8% 14% 6% 1	1337
	11th to 20th	Day	61% 9% 13% 11% 6% 1	1472
	21st to end	Day	46% 16% 13% 14% 10% 1	2090
January	1st to 10th	Night	63% 12% 12% 8% 4 1	5046
	11th to 20th	Night	53% 8% 8% 10% 17% 4	4761
	21st to end	Night	65% 13% 10% 9% 3 1	4862
February	1st to 10th	Night	65% 8% 10% 9% 7% 2	2660
	11th to 20th	Night	61% 10% 12% 10% 5% 1	2512
	21st to end	Night	55% 8% 12% 16% 7% 2	1890
March	1st to 10th	Night	53% 16% 12% 11% 7% 1	3736
	11th to 20th	Night	47% 11% 18% 19% 4	3728
	21st to end	Night	57% 14% 11% 10% 7%	3488
April	1st to 10th	Night	62% 13% 13% 11% 2	1900
	11th to 20th	Night	54% 11% 15% 15% 5%	1743
	21st to end	Night	54% 12% 12% 17% 4	1572
May	1st to 10th	Night	56% 11% 14% 17% 3	2540
	11th to 20th	Night	54% 14% 12% 14% 7%	2295
	21st to end	Night	63% 14% 10% 10% 3	2414
June	1st to 10th	Night	55% 9% 15% 13% 6% 1	1141
	11th to 20th	Night	63% 11% 13% 10% 3	1140
	21st to end	Night	49% 13% 16% 16% 5% 1	1140
July	1st to 10th	Night	38% 7% 11% 22% 21% 1	1870
	11th to 20th	Night	34% 6% 14% 25% 21% 1	1914
	21st to end	Night	45% 7% 14% 21% 9% 5%	2611
August	1st to 10th	Night	43% 9% 14% 31% 3	2521
	11th to 20th	Night	46% 9% 19% 21% 5%	2521
	21st to end	Night	51% 7% 21% 17% 4	3197
September	1st to 10th	Night	44% 9% 18% 22% 6% 1	1900
	11th to 20th	Night	48% 9% 17% 18% 8%	1968
	21st to end	Night	48% 13% 16% 17% 6% 1	2090
October	1st to 10th	Night	62% 7% 16% 12% 2	3728
	11th to 20th	Night	58% 7% 18% 15% 2	4042
	21st to end	Night	61% 7% 19% 10% 4	4457
November	1st to 10th	Night	64% 10% 14% 8% 3 1	2650
	11th to 20th	Night	58% 12% 14% 9% 6% 1	2996
	21st to end	Night	60% 11% 12% 10% 5% 2	3000
December	1st to 10th	Night	58% 8% 12% 12% 8% 1	2878
	11th to 20th	Night	61% 12% 13% 9% 5%	3717
	21st to end	Night	48% 11% 18% 15% 7% 1	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	11% 21% 32% 28% 6% 2	180
	11th to 20th	Day	13% 19% 34% 26% 4 3	180
	21st to end	Day	19% 19% 37% 17% 7% 2	198
February	1st to 10th	Day	22% 21% 34% 17% 4 1	180
	11th to 20th	Day	15% 21% 32% 21% 9% 2	255
	21st to end	Day	15% 24% 37% 15% 8% 1	379
March	1st to 10th	Day	20% 25% 30% 15% 9% 1	460
	11th to 20th	Day	18% 27% 32% 16% 6% 2	460
	21st to end	Day	21% 23% 28% 18% 8% 2	506
April	1st to 10th	Day	26% 20% 31% 16% 5% 1	460
	11th to 20th	Day	19% 19% 32% 21% 8% 2	452
	21st to end	Day	22% 24% 26% 18% 8% 2	460
May	1st to 10th	Day	23% 17% 32% 19% 7% 2	463
	11th to 20th	Day	16% 14% 27% 28% 13% 2	616
	21st to end	Day	23% 13% 23% 24% 16% 2	734
June	1st to 10th	Day	28% 17% 30% 18% 6% 1	865
	11th to 20th	Day	32% 14% 28% 17% 8% 1	870
	21st to end	Day	24% 12% 26% 23% 13% 2	870
July	1st to 10th	Day	23% 12% 28% 23% 12% 1	856
	11th to 20th	Day	22% 13% 29% 25% 9% 2	828
	21st to end	Day	21% 16% 27% 21% 14% 3	568
August	1st to 10th	Day	19% 10% 31% 24% 13% 3	487
	11th to 20th	Day	19% 19% 34% 16% 9% 1	477
	21st to end	Day	24% 16% 33% 17% 8% 2	539
September	1st to 10th	Day	28% 18% 29% 17% 7% 1	490
	11th to 20th	Day	23% 19% 28% 22% 6% 2	490
	21st to end	Day	34% 24% 21% 16% 3 1	490
October	1st to 10th	Day	31% 19% 26% 15% 7% 2	490
	11th to 20th	Day	29% 23% 24% 17% 6% 2	331
	21st to end	Day	24% 20% 32% 18% 5% 1	330
November	1st to 10th	Day	32% 22% 30% 10% 5% 2	240
	11th to 20th	Day	23% 21% 33% 18% 4 2	200
	21st to end	Day	20% 23% 26% 20% 9% 3	200
December	1st to 10th	Day	12% 24% 29% 21% 9% 5%	182
	11th to 20th	Day	12% 20% 42% 21% 5% 1	180
	21st to end	Day	8% 17% 37% 26% 9% 3	198
January	1st to 10th	Night	13% 20% 43% 18% 4 1	1040
	11th to 20th	Night	11% 19% 44% 19% 6% 1	903
	21st to end	Night	14% 23% 40% 17% 6% 1	836
February	1st to 10th	Night	14% 20% 34% 24% 7% 1	760
	11th to 20th	Night	10% 16% 41% 25% 7% 1	744
	21st to end	Night	10% 14% 37% 28% 9% 2	628
March	1st to 10th	Night	9% 17% 42% 22% 9% 1	760
	11th to 20th	Night	8% 21% 41% 22% 8% 1	760
	21st to end	Night	10% 15% 34% 29% 11% 2	836
April	1st to 10th	Night	11% 18% 30% 31% 9% 1	760
	11th to 20th	Night	9% 15% 37% 26% 13% 1	615
	21st to end	Night	16% 14% 30% 31% 9% 1	432
May	1st to 10th	Night	17% 8% 22% 40% 12% 1	380
	11th to 20th	Night	10% 7% 24% 36% 20% 2	374
	21st to end	Night	19% 11% 23% 26% 20% 1	411
June	1st to 10th	Night	22% 7% 31% 25% 14% 1	380
	11th to 20th	Night	23% 9% 28% 27% 12% 1	380
	21st to end	Night	15% 9% 28% 29% 19% 1	380
July	1st to 10th	Night	20% 5% 20% 39% 17%	370
	11th to 20th	Night	18% 10% 22% 32% 18%	368
	21st to end	Night	14% 8% 19% 39% 19%	416
August	1st to 10th	Night	16% 4 18% 36% 24% 2	378
	11th to 20th	Night	14% 8% 22% 37% 19% 1	376
	21st to end	Night	20% 10% 27% 32% 11%	652
September	1st to 10th	Night	20% 11% 27% 27% 15% 1	760
	11th to 20th	Night	18% 9% 26% 29% 17% 1	760
	21st to end	Night	24% 14% 28% 22% 10% 1	760
October	1st to 10th	Night	21% 13% 31% 24% 9% 1	760
	11th to 20th	Night	18% 17% 34% 25% 6% 1	760
	21st to end	Night	17% 17% 40% 21% 5% 1	836
November	1st to 10th	Night	19% 20% 40% 16% 5% 1	780
	11th to 20th	Night	15% 23% 43% 15% 4 1	996
	21st to end	Night	13% 20% 43% 18% 4 2	1000
December	1st to 10th	Night	12% 21% 40% 20% 7% 1	960
	11th to 20th	Night	11% 18% 46% 19% 6%	1026
	21st to end	Night	8% 17% 47% 20% 7% 1	1144

Page generated at 2024-11-29 08:43:05. Version ac07

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