Milo McIver State Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Milo McIver State Park clear sky chart from 2005-11-06 to 2025-12-18.

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	19% 9% 3 6% 4 4 4 3 4 5% 38%	136401
	Night	23% 10% 3 6% 4 4 4 3 4 5% 35%	131974
Transparency	Day	48% 6% 10% 18% 13% 5%	131170
	Night	52% 6% 10% 16% 12% 4	128202
Seeing	Day	25% 12% 23% 26% 12% 2	15981
	Night	29% 9% 17% 28% 16% 2	24987

By Month

Percentage Cloud Cover SW (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	37% 17% 4 8% 5% 4 4 3 3 4 12%	3639
	11th to 20th	Day	27% 14% 3 6% 3 3 3 2 5% 6% 27%	3640
	21st to end	Day	28% 10% 3 5% 4 3 3 3 4 4 32%	4349
February	1st to 10th	Day	29% 16% 3 7% 5% 4 4 4 5% 5% 18%	1800
	11th to 20th	Day	28% 16% 4 9% 6% 3 4 3 4 4 20%	1755
	21st to end	Day	28% 19% 3 8% 4 4 4 2 3 5% 19%	1585
March	1st to 10th	Day	18% 12% 4 10% 6% 5% 7% 4 6% 7% 21%	4688
	11th to 20th	Day	24% 16% 4 8% 5% 5% 4 3 3 3 26%	5000
	21st to end	Day	25% 14% 4 11% 6% 6% 6% 4 5% 7% 12%	5647
April	1st to 10th	Day	28% 16% 4 9% 6% 4 4 3 4 5% 17%	2400
	11th to 20th	Day	24% 14% 4 8% 5% 3 4 3 5% 4 25%	2369
	21st to end	Day	25% 13% 3 8% 5% 4 4 3 6% 5% 24%	2565
May	1st to 10th	Day	19% 9% 3 6% 4 4 4 3 4 5% 39%	6266
	11th to 20th	Day	20% 11% 4 9% 5% 5% 4 3 5% 5% 29%	6277
	21st to end	Day	20% 9% 3 7% 4 4 5% 4 6% 7% 32%	6902
June	1st to 10th	Day	25% 9% 3 6% 5% 4 3 3 5% 6% 33%	2800
	11th to 20th	Day	24% 11% 2 7% 5% 4 5% 5% 6% 6% 26%	2800
	21st to end	Day	11% 6% 2 6% 4 4 4 3 4 6% 50%	2800
July	1st to 10th	Day	5% 3 1 3 2 2 3 2 3 4 71%	6319
	11th to 20th	Day	3 2 1 2 2 2 2 1 3 4 79%	6320
	21st to end	Day	5% 3 1 2 2 2 2 2 3 5% 72%	6880
August	1st to 10th	Day	5% 4 1 4 3 3 4 3 4 6% 63%	5872
	11th to 20th	Day	7% 4 2 6% 3 4 4 4 5% 7% 54%	5796
	21st to end	Day	8% 5% 2 5% 3 4 4 4 6% 7% 52%	6116
September	1st to 10th	Day	8% 4 2 4 3 3 4 3 5% 7% 58%	2400
	11th to 20th	Day	13% 8% 2 6% 4 4 4 4 5% 5% 44%	2400
	21st to end	Day	17% 6% 2 6% 3 4 4 3 4 7% 46%	2114
October	1st to 10th	Day	18% 6% 2 4 3 3 3 3 4 6% 49%	3280
	11th to 20th	Day	21% 6% 3 7% 4 4 4 4 6% 6% 35%	3261
	21st to end	Day	27% 10% 3 8% 5% 5% 4 4 5% 7% 23%	3444
November	1st to 10th	Day	32% 10% 4 9% 4 4 4 4 5% 6% 19%	1769
	11th to 20th	Day	33% 10% 3 8% 5% 3 4 4 5% 5% 19%	1680
	21st to end	Day	28% 12% 3 8% 5% 4 4 4 5% 5% 23%	1680
December	1st to 10th	Day	23% 9% 3 6% 3 3 4 3 4 6% 37%	2700
	11th to 20th	Day	31% 14% 4 9% 6% 5% 4 4 5% 4 14%	3084
	21st to end	Day	34% 17% 4 9% 5% 4 3 3 4 3 14%	4004
January	1st to 10th	Night	35% 17% 3 9% 5% 4 4 3 3 4 14%	6306
	11th to 20th	Night	28% 15% 3 6% 3 3 3 2 4 5% 30%	6320
	21st to end	Night	28% 10% 3 6% 4 3 2 2 3 4 34%	6620
February	1st to 10th	Night	28% 16% 4 8% 5% 4 4 3 4 5% 18%	2600
	11th to 20th	Night	32% 14% 3 7% 4 3 4 3 4 5% 23%	2532
	21st to end	Night	29% 19% 3 5% 4 3 3 3 4 6% 20%	2045
March	1st to 10th	Night	18% 14% 4 9% 6% 5% 6% 4 6% 6% 22%	5204
	11th to 20th	Night	24% 13% 3 8% 4 4 4 3 3 4 30%	5000
	21st to end	Night	28% 17% 4 9% 6% 6% 4 3 5% 6% 13%	5327
April	1st to 10th	Night	28% 17% 3 7% 5% 4 4 3 3 5% 19%	2000
	11th to 20th	Night	23% 13% 4 6% 4 3 4 3 4 6% 30%	1979
	21st to end	Night	28% 12% 3 7% 3 4 3 3 4 5% 26%	1832
May	1st to 10th	Night	24% 10% 2 5% 3 3 3 3 4 6% 38%	3694
	11th to 20th	Night	27% 11% 2 8% 4 3 3 3 4 5% 30%	3616
	21st to end	Night	23% 9% 3 7% 4 4 4 4 5% 8% 30%	3972
June	1st to 10th	Night	22% 9% 3 7% 3 4 3 3 4 7% 36%	1600
	11th to 20th	Night	24% 10% 3 7% 5% 4 4 3 4 5% 31%	1600
	21st to end	Night	13% 6% 3 5% 4 3 3 3 5% 5% 51%	1600
July	1st to 10th	Night	8% 3 1 2 2 2 2 3 4 4 70%	3640
	11th to 20th	Night	3 2 1 2 2 2 2 1 3 4 79%	3640
	21st to end	Night	4 3 1 2 2 2 2 2 4 6% 72%	3970
August	1st to 10th	Night	7% 4 1 4 3 3 3 3 5% 7% 60%	3933
	11th to 20th	Night	14% 7% 2 5% 3 3 4 2 4 5% 52%	4052
	21st to end	Night	10% 5% 2 5% 3 3 4 3 4 6% 56%	4877
September	1st to 10th	Night	8% 4 1 4 2 2 3 3 4 5% 62%	2000
	11th to 20th	Night	15% 7% 2 6% 4 4 4 2 4 5% 47%	2000
	21st to end	Night	15% 6% 2 5% 3 4 3 2 5% 7% 48%	2282
October	1st to 10th	Night	17% 6% 2 5% 3 3 3 2 4 6% 50%	3920
	11th to 20th	Night	17% 8% 3 7% 4 4 4 4 6% 7% 36%	3897
	21st to end	Night	27% 10% 3 8% 5% 4 4 3 4 5% 25%	4361
November	1st to 10th	Night	33% 10% 3 7% 5% 4 4 3 4 5% 21%	2749
	11th to 20th	Night	36% 11% 3 7% 5% 4 3 3 4 4 21%	2940
	21st to end	Night	28% 11% 3 7% 5% 4 4 3 4 5% 27%	2940
December	1st to 10th	Night	21% 9% 3 6% 3 3 3 3 4 6% 39%	4700
	11th to 20th	Night	32% 14% 4 9% 5% 4 4 3 4 5% 14%	5274
	21st to end	Night	32% 14% 4 8% 6% 4 4 3 4 4 15%	6952

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	77% 5% 5% 7% 5% 1	3639
	11th to 20th	Day	58% 4 5% 20% 11% 3	3640
	21st to end	Day	55% 5% 5% 14% 15% 6%	4349
February	1st to 10th	Day	68% 7% 9% 9% 6% 1	1800
	11th to 20th	Day	70% 5% 7% 10% 5% 3	1764
	21st to end	Day	70% 4 8% 8% 8% 2	1585
March	1st to 10th	Day	59% 8% 10% 15% 7%	4688
	11th to 20th	Day	64% 5% 5% 17% 9%	5000
	21st to end	Day	70% 9% 10% 8% 3	5647
April	1st to 10th	Day	70% 8% 8% 11% 3	2400
	11th to 20th	Day	63% 6% 8% 13% 8% 2	2372
	21st to end	Day	63% 7% 9% 12% 7% 2	2565
May	1st to 10th	Day	47% 7% 8% 23% 14%	6266
	11th to 20th	Day	54% 8% 13% 17% 7%	6280
	21st to end	Day	50% 10% 20% 17% 3	6904
June	1st to 10th	Day	54% 6% 15% 18% 7%	2800
	11th to 20th	Day	58% 8% 14% 13% 7%	2800
	21st to end	Day	37% 4 15% 28% 11% 4	2800
July	1st to 10th	Day	18% 4 8% 29% 19% 23%	6251
	11th to 20th	Day	13% 2 6% 20% 38% 21%	6245
	21st to end	Day	16% 3 15% 35% 26% 5%	6681
August	1st to 10th	Day	21% 4 9% 28% 27% 12%	4276
	11th to 20th	Day	26% 6% 17% 33% 14% 5%	4195
	21st to end	Day	32% 5% 11% 23% 19% 11%	4407
September	1st to 10th	Day	26% 4 10% 28% 20% 13%	2400
	11th to 20th	Day	40% 6% 12% 19% 15% 8%	2400
	21st to end	Day	40% 5% 12% 21% 15% 8%	2114
October	1st to 10th	Day	38% 4 7% 23% 21% 7%	3280
	11th to 20th	Day	50% 5% 14% 17% 11% 2	3261
	21st to end	Day	59% 5% 8% 18% 10% 1	3444
November	1st to 10th	Day	66% 6% 9% 13% 5% 1	1769
	11th to 20th	Day	66% 8% 8% 10% 6% 2	1680
	21st to end	Day	62% 6% 7% 8% 15% 2	1680
December	1st to 10th	Day	51% 4 8% 9% 23% 5%	2700
	11th to 20th	Day	72% 6% 9% 8% 5%	3084
	21st to end	Day	75% 5% 8% 9% 2 1	4004
January	1st to 10th	Night	76% 4 6% 8% 5% 1	6306
	11th to 20th	Night	58% 4 6% 19% 9% 4	6320
	21st to end	Night	55% 4 4 13% 15% 8%	6620
February	1st to 10th	Night	69% 6% 8% 9% 7% 2	2600
	11th to 20th	Night	66% 6% 7% 11% 7% 3	2534
	21st to end	Night	67% 6% 8% 10% 7% 2	2045
March	1st to 10th	Night	60% 8% 10% 15% 6% 1	5204
	11th to 20th	Night	59% 6% 8% 17% 9% 1	5000
	21st to end	Night	70% 8% 10% 11% 1	5327
April	1st to 10th	Night	69% 6% 11% 10% 4	2000
	11th to 20th	Night	58% 8% 12% 12% 7% 3	1979
	21st to end	Night	61% 7% 11% 13% 6% 2	1832
May	1st to 10th	Night	49% 6% 7% 25% 12% 1	3691
	11th to 20th	Night	57% 9% 13% 17% 4 1	3616
	21st to end	Night	50% 11% 19% 15% 5%	3972
June	1st to 10th	Night	52% 6% 16% 19% 6% 1	1600
	11th to 20th	Night	57% 6% 14% 18% 6% 1	1600
	21st to end	Night	36% 7% 16% 26% 10% 5%	1600
July	1st to 10th	Night	20% 4 8% 26% 24% 18%	3600
	11th to 20th	Night	13% 2 8% 18% 40% 18%	3592
	21st to end	Night	14% 3 20% 32% 26% 5%	3857
August	1st to 10th	Night	17% 3 9% 33% 26% 11%	2854
	11th to 20th	Night	32% 5% 21% 25% 12% 6%	2929
	21st to end	Night	31% 4 10% 26% 15% 12%	3509
September	1st to 10th	Night	25% 6% 13% 25% 18% 12%	2000
	11th to 20th	Night	41% 6% 9% 21% 12% 11%	2000
	21st to end	Night	36% 7% 12% 20% 16% 9%	2282
October	1st to 10th	Night	38% 3 6% 24% 25% 4	3920
	11th to 20th	Night	46% 6% 13% 19% 13% 3	3897
	21st to end	Night	61% 4 8% 15% 10% 3	4361
November	1st to 10th	Night	66% 6% 7% 11% 9% 1	2749
	11th to 20th	Night	67% 7% 7% 9% 7% 3	2940
	21st to end	Night	60% 6% 7% 10% 13% 4	2940
December	1st to 10th	Night	47% 4 8% 14% 22% 4	4700
	11th to 20th	Night	72% 5% 9% 8% 5% 1	5274
	21st to end	Night	69% 9% 10% 8% 3 1	6952

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	48% 16% 15% 16% 6%	200
	11th to 20th	Day	39% 11% 30% 13% 7% 2	200
	21st to end	Day	37% 11% 19% 20% 10% 2	370
February	1st to 10th	Day	41% 16% 17% 19% 7% 1	400
	11th to 20th	Day	37% 17% 26% 16% 3 1	395
	21st to end	Day	40% 15% 23% 19% 4	381
March	1st to 10th	Day	34% 17% 27% 17% 5%	500
	11th to 20th	Day	34% 16% 23% 19% 6% 1	500
	21st to end	Day	37% 20% 22% 17% 4	550
April	1st to 10th	Day	37% 17% 20% 19% 7% 1	500
	11th to 20th	Day	30% 18% 28% 15% 7% 2	492
	21st to end	Day	28% 15% 27% 21% 8% 1	500
May	1st to 10th	Day	23% 16% 26% 23% 9% 3	503
	11th to 20th	Day	30% 14% 21% 22% 10% 2	528
	21st to end	Day	26% 9% 24% 25% 13% 3	573
June	1st to 10th	Day	24% 10% 20% 28% 14% 4	530
	11th to 20th	Day	23% 15% 29% 24% 9% 1	530
	21st to end	Day	12% 7% 27% 35% 16% 4	530
July	1st to 10th	Day	7% 5% 24% 43% 17% 3	526
	11th to 20th	Day	4 7% 25% 40% 20% 4	524
	21st to end	Day	6% 3 20% 44% 21% 6%	575
August	1st to 10th	Day	6% 5% 16% 49% 18% 7%	527
	11th to 20th	Day	5% 5% 21% 38% 25% 6%	517
	21st to end	Day	8% 8% 26% 36% 17% 5%	583
September	1st to 10th	Day	10% 7% 26% 35% 19% 3	530
	11th to 20th	Day	16% 8% 21% 35% 17% 3	530
	21st to end	Day	18% 10% 26% 30% 14% 2	530
October	1st to 10th	Day	22% 11% 23% 27% 15% 2	530
	11th to 20th	Day	26% 11% 21% 27% 14% 1	530
	21st to end	Day	34% 13% 20% 22% 9% 2	518
November	1st to 10th	Day	37% 15% 17% 22% 7% 1	285
	11th to 20th	Day	36% 14% 25% 15% 8% 2	220
	21st to end	Day	32% 15% 19% 24% 10%	220
December	1st to 10th	Day	37% 15% 18% 16% 11% 3	220
	11th to 20th	Day	48% 14% 20% 13% 5%	214
	21st to end	Day	49% 13% 18% 13% 7%	220
January	1st to 10th	Night	44% 13% 20% 17% 6% 1	800
	11th to 20th	Night	39% 11% 22% 20% 9%	800
	21st to end	Night	35% 10% 23% 24% 8% 1	880
February	1st to 10th	Night	36% 11% 21% 26% 5% 1	800
	11th to 20th	Night	39% 13% 17% 23% 7%	784
	21st to end	Night	41% 13% 19% 22% 6%	660
March	1st to 10th	Night	33% 13% 19% 25% 10% 1	800
	11th to 20th	Night	33% 11% 20% 26% 10% 1	800
	21st to end	Night	38% 13% 17% 22% 9% 1	880
April	1st to 10th	Night	37% 11% 17% 23% 11% 1	800
	11th to 20th	Night	31% 10% 19% 25% 13% 2	791
	21st to end	Night	35% 10% 12% 29% 12% 1	632
May	1st to 10th	Night	27% 10% 14% 32% 15% 2	428
	11th to 20th	Night	26% 8% 13% 29% 23% 1	394
	21st to end	Night	28% 6% 16% 28% 20% 2	433
June	1st to 10th	Night	27% 5% 15% 30% 22% 2	400
	11th to 20th	Night	27% 9% 17% 32% 16% 1	400
	21st to end	Night	15% 5% 13% 39% 26% 1	400
July	1st to 10th	Night	9% 3 9% 41% 37% 1	390
	11th to 20th	Night	6% 2 13% 46% 32% 1	388
	21st to end	Night	4 2 7% 42% 42% 3	438
August	1st to 10th	Night	7% 2 7% 33% 45% 6%	547
	11th to 20th	Night	8% 1 9% 32% 43% 7%	594
	21st to end	Night	8% 4 13% 41% 30% 4	820
September	1st to 10th	Night	11% 3 15% 36% 33% 3	800
	11th to 20th	Night	16% 5% 12% 34% 29% 4	800
	21st to end	Night	18% 5% 15% 34% 26% 3	800
October	1st to 10th	Night	24% 5% 15% 34% 20% 2	800
	11th to 20th	Night	24% 8% 15% 33% 18% 2	800
	21st to end	Night	30% 10% 22% 25% 11% 2	880
November	1st to 10th	Night	39% 10% 18% 26% 6%	820
	11th to 20th	Night	42% 11% 21% 20% 5%	840
	21st to end	Night	32% 11% 22% 28% 7%	840
December	1st to 10th	Night	35% 11% 22% 24% 7% 1	840
	11th to 20th	Night	41% 12% 21% 20% 6%	828
	21st to end	Night	45% 13% 22% 16% 4 1	880

Page generated at 2025-12-14 22:13:50. Version ac07

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