James Baird State Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the James Baird State Park clear sky chart from 2005-11-06 to 2025-04-11.

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	16% 7% 3 7% 4 4 4 4 5% 7% 38%	113283
	Night	17% 8% 3 7% 4 4 4 3 5% 6% 38%	114964
Transparency	Day	43% 6% 12% 22% 15% 2	116845
	Night	44% 6% 12% 21% 15% 2	119566
Seeing	Day	23% 16% 29% 20% 9% 3	15401
	Night	21% 14% 30% 26% 8% 1	24636

By Month

Percentage Cloud Cover NE (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	12% 8% 3 8% 6% 5% 5% 4 5% 6% 39%	3597
	11th to 20th	Day	13% 10% 3 9% 6% 5% 4 3 6% 5% 36%	3570
	21st to end	Day	18% 8% 3 8% 4 4 4 4 5% 5% 37%	4190
February	1st to 10th	Day	17% 9% 3 8% 5% 6% 4 4 5% 7% 33%	1802
	11th to 20th	Day	14% 9% 3 8% 5% 4 4 4 5% 6% 37%	1948
	21st to end	Day	19% 9% 3 6% 5% 4 4 3 5% 5% 38%	1650
March	1st to 10th	Day	22% 9% 3 7% 4 4 3 3 4 4 37%	4476
	11th to 20th	Day	12% 8% 3 7% 4 4 4 3 5% 6% 43%	4722
	21st to end	Day	19% 8% 2 7% 4 4 4 4 4 6% 36%	5961
April	1st to 10th	Day	19% 10% 4 6% 5% 3 4 3 5% 6% 35%	2400
	11th to 20th	Day	17% 7% 2 6% 5% 5% 4 4 4 7% 39%	2254
	21st to end	Day	20% 6% 2 5% 5% 4 5% 3 5% 6% 39%	2341
May	1st to 10th	Day	24% 9% 3 6% 4 3 4 3 5% 7% 31%	4106
	11th to 20th	Day	20% 8% 3 8% 4 5% 5% 4 5% 7% 32%	4397
	21st to end	Day	13% 5% 2 5% 4 4 5% 4 7% 9% 43%	4837
June	1st to 10th	Day	17% 5% 2 6% 4 4 6% 4 7% 9% 36%	2660
	11th to 20th	Day	14% 6% 3 7% 4 4 5% 5% 7% 9% 35%	2660
	21st to end	Day	12% 6% 2 7% 5% 5% 5% 5% 6% 8% 38%	2660
July	1st to 10th	Day	9% 7% 3 8% 5% 5% 6% 4 7% 9% 37%	4440
	11th to 20th	Day	10% 6% 2 7% 5% 5% 5% 5% 6% 10% 39%	4440
	21st to end	Day	13% 7% 3 8% 5% 5% 5% 5% 6% 8% 35%	4814
August	1st to 10th	Day	19% 7% 3 7% 5% 6% 5% 5% 6% 7% 31%	4282
	11th to 20th	Day	12% 6% 2 6% 4 4 5% 5% 7% 8% 41%	3730
	21st to end	Day	11% 6% 2 6% 4 5% 4 4 6% 10% 44%	4180
September	1st to 10th	Day	13% 8% 2 5% 4 4 5% 4 6% 7% 43%	2280
	11th to 20th	Day	13% 5% 1 5% 4 4 5% 3 5% 6% 50%	2190
	21st to end	Day	17% 6% 3 6% 4 3 5% 4 5% 7% 41%	2090
October	1st to 10th	Day	20% 7% 2 6% 4 4 4 3 5% 6% 41%	1995
	11th to 20th	Day	14% 6% 2 6% 4 4 4 4 4 7% 44%	1900
	21st to end	Day	22% 6% 2 6% 5% 4 5% 4 5% 6% 36%	1909
November	1st to 10th	Day	13% 6% 2 5% 4 3 3 3 4 7% 49%	1761
	11th to 20th	Day	17% 7% 2 5% 3 4 3 3 6% 6% 43%	1800
	21st to end	Day	18% 8% 2 5% 4 4 3 3 5% 7% 41%	1695
December	1st to 10th	Day	17% 8% 3 5% 4 4 4 3 5% 6% 39%	2600
	11th to 20th	Day	21% 8% 2 6% 3 3 4 3 5% 7% 39%	2986
	21st to end	Day	18% 10% 4 9% 5% 4 3 3 4 7% 33%	3960
January	1st to 10th	Night	14% 7% 3 9% 5% 5% 4 3 5% 6% 38%	6349
	11th to 20th	Night	12% 8% 3 9% 6% 5% 5% 4 5% 7% 35%	6315
	21st to end	Night	18% 10% 3 7% 5% 4 4 3 5% 6% 35%	6749
February	1st to 10th	Night	15% 11% 3 7% 5% 4 4 4 4 6% 37%	2596
	11th to 20th	Night	15% 8% 3 8% 5% 4 4 4 6% 6% 35%	2338
	21st to end	Night	17% 8% 3 7% 5% 4 4 4 4 6% 37%	1980
March	1st to 10th	Night	20% 8% 2 5% 4 4 4 3 4 6% 39%	5364
	11th to 20th	Night	15% 9% 3 7% 4 4 4 3 5% 6% 40%	5221
	21st to end	Night	19% 10% 3 7% 4 4 4 3 5% 5% 36%	4969
April	1st to 10th	Night	19% 9% 3 9% 6% 4 4 5% 5% 7% 32%	2000
	11th to 20th	Night	20% 8% 2 6% 4 4 4 3 4 6% 38%	1882
	21st to end	Night	20% 9% 3 6% 3 3 4 3 3 6% 40%	1838
May	1st to 10th	Night	26% 9% 2 7% 4 4 4 3 4 7% 30%	2834
	11th to 20th	Night	20% 9% 3 9% 5% 5% 3 4 4 6% 33%	2511
	21st to end	Night	14% 6% 2 6% 4 4 4 3 6% 9% 42%	2738
June	1st to 10th	Night	15% 6% 3 5% 4 5% 5% 3 6% 7% 41%	1520
	11th to 20th	Night	14% 8% 2 5% 4 4 5% 4 6% 9% 40%	1520
	21st to end	Night	11% 5% 2 6% 4 3 5% 4 7% 11% 41%	1520
July	1st to 10th	Night	10% 5% 2 7% 4 6% 6% 5% 8% 8% 38%	2520
	11th to 20th	Night	13% 6% 3 7% 4 5% 5% 4 7% 9% 37%	2520
	21st to end	Night	15% 8% 2 7% 4 4 4 4 5% 7% 39%	2739
August	1st to 10th	Night	20% 7% 3 7% 5% 5% 5% 5% 5% 7% 31%	2614
	11th to 20th	Night	13% 7% 3 7% 5% 4 5% 4 6% 7% 39%	3097
	21st to end	Night	12% 4 2 5% 3 3 5% 3 5% 7% 50%	3476
September	1st to 10th	Night	15% 7% 2 6% 4 3 3 3 4 8% 45%	1900
	11th to 20th	Night	12% 5% 2 4 3 4 3 2 5% 7% 53%	1990
	21st to end	Night	17% 6% 3 5% 3 3 4 4 6% 6% 44%	2090
October	1st to 10th	Night	20% 7% 3 6% 4 3 3 3 5% 6% 40%	2182
	11th to 20th	Night	14% 6% 2 6% 3 4 4 4 5% 7% 44%	2280
	21st to end	Night	21% 8% 2 7% 4 4 3 3 5% 6% 37%	2688
November	1st to 10th	Night	13% 8% 2 6% 3 3 4 3 5% 7% 46%	2537
	11th to 20th	Night	19% 8% 2 5% 4 3 3 3 5% 5% 43%	2600
	21st to end	Night	15% 8% 3 6% 5% 4 3 3 5% 8% 41%	2703
December	1st to 10th	Night	17% 9% 3 6% 4 4 4 3 5% 6% 39%	4580
	11th to 20th	Night	24% 9% 3 6% 4 3 3 3 5% 5% 34%	5208
	21st to end	Night	19% 12% 4 7% 5% 3 4 3 5% 5% 33%	6996

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	44% 4 9% 27% 13% 2	3598
	11th to 20th	Day	48% 4 10% 21% 12% 5%	3600
	21st to end	Day	48% 6% 8% 23% 14% 1	4190
February	1st to 10th	Day	49% 7% 12% 18% 13% 1	1802
	11th to 20th	Day	46% 5% 10% 21% 15% 3	1957
	21st to end	Day	49% 4 11% 21% 12% 2	1650
March	1st to 10th	Day	50% 4 10% 16% 11% 8%	4479
	11th to 20th	Day	39% 5% 14% 29% 9% 4	4722
	21st to end	Day	48% 5% 8% 13% 21% 5%	5961
April	1st to 10th	Day	50% 4 10% 20% 13% 3	2400
	11th to 20th	Day	44% 5% 11% 21% 16% 2	2254
	21st to end	Day	46% 5% 11% 20% 15% 3	2341
May	1st to 10th	Day	51% 7% 14% 15% 11% 1	4120
	11th to 20th	Day	50% 8% 13% 19% 9% 1	4401
	21st to end	Day	34% 9% 13% 26% 17% 1	4837
June	1st to 10th	Day	42% 8% 14% 21% 13% 1	2660
	11th to 20th	Day	44% 7% 13% 24% 10% 2	2660
	21st to end	Day	43% 9% 12% 23% 13% 1	2660
July	1st to 10th	Day	43% 8% 11% 20% 16% 1	4370
	11th to 20th	Day	39% 8% 16% 23% 13% 1	4365
	21st to end	Day	48% 7% 12% 17% 15% 1	4661
August	1st to 10th	Day	49% 8% 13% 21% 8%	4268
	11th to 20th	Day	37% 8% 16% 29% 10%	3766
	21st to end	Day	35% 6% 12% 31% 15% 1	4180
September	1st to 10th	Day	39% 8% 10% 24% 18% 2	2280
	11th to 20th	Day	35% 6% 9% 25% 24% 2	2190
	21st to end	Day	42% 7% 11% 21% 17% 3	2090
October	1st to 10th	Day	40% 6% 8% 18% 25% 3	3320
	11th to 20th	Day	31% 5% 10% 25% 26% 4	3140
	21st to end	Day	32% 5% 15% 25% 20% 3	3121
November	1st to 10th	Day	36% 6% 13% 26% 17% 3	1761
	11th to 20th	Day	40% 5% 12% 22% 19% 3	1800
	21st to end	Day	44% 4 14% 27% 10% 2	1695
December	1st to 10th	Day	44% 4 17% 27% 8%	2600
	11th to 20th	Day	45% 4 15% 20% 14% 2	2986
	21st to end	Day	51% 4 8% 20% 14% 2	3960
January	1st to 10th	Night	44% 6% 9% 23% 16% 2	6349
	11th to 20th	Night	46% 5% 14% 19% 12% 5%	6360
	21st to end	Night	49% 4 10% 17% 16% 4	6749
February	1st to 10th	Night	48% 6% 12% 21% 11% 2	2596
	11th to 20th	Night	46% 6% 11% 17% 17% 4	2340
	21st to end	Night	46% 5% 10% 22% 14% 4	1980
March	1st to 10th	Night	45% 6% 12% 17% 14% 6%	5374
	11th to 20th	Night	43% 5% 16% 22% 10% 4	5222
	21st to end	Night	49% 4 6% 13% 23% 4	4969
April	1st to 10th	Night	51% 6% 10% 17% 14% 2	2000
	11th to 20th	Night	48% 5% 10% 19% 18% 1	1882
	21st to end	Night	46% 5% 8% 21% 15% 3	1838
May	1st to 10th	Night	54% 8% 11% 15% 10% 1	2840
	11th to 20th	Night	51% 8% 12% 17% 9% 1	2512
	21st to end	Night	38% 8% 15% 23% 13% 2	2739
June	1st to 10th	Night	42% 8% 11% 22% 16% 2	1520
	11th to 20th	Night	39% 8% 17% 24% 10% 1	1520
	21st to end	Night	36% 9% 15% 26% 14% 1	1520
July	1st to 10th	Night	40% 9% 15% 19% 15% 2	2480
	11th to 20th	Night	43% 7% 13% 24% 12%	2472
	21st to end	Night	45% 8% 13% 16% 18% 2	2651
August	1st to 10th	Night	51% 10% 13% 17% 9% 1	2604
	11th to 20th	Night	42% 7% 13% 28% 9%	3127
	21st to end	Night	32% 6% 12% 35% 15% 1	3476
September	1st to 10th	Night	40% 6% 10% 26% 17% 1	1900
	11th to 20th	Night	31% 6% 10% 25% 26% 2	1990
	21st to end	Night	41% 6% 10% 21% 22% 1	2090
October	1st to 10th	Night	42% 7% 9% 22% 18% 1	3637
	11th to 20th	Night	29% 5% 10% 28% 26% 2	3779
	21st to end	Night	34% 5% 13% 29% 18% 1	4426
November	1st to 10th	Night	37% 6% 11% 22% 20% 3	2537
	11th to 20th	Night	43% 5% 9% 21% 19% 4	2600
	21st to end	Night	41% 6% 15% 28% 10% 1	2703
December	1st to 10th	Night	44% 5% 13% 29% 8% 1	4580
	11th to 20th	Night	50% 4 13% 16% 15% 2	5208
	21st to end	Night	51% 4 10% 16% 15% 3	6996

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	28% 29% 24% 15% 5%	200
	11th to 20th	Day	36% 25% 25% 12% 3	200
	21st to end	Day	24% 27% 33% 11% 3 2	270
February	1st to 10th	Day	36% 25% 28% 8% 2	302
	11th to 20th	Day	30% 25% 32% 13%	496
	21st to end	Day	31% 22% 31% 13% 2	414
March	1st to 10th	Day	30% 21% 32% 14% 3	500
	11th to 20th	Day	29% 23% 30% 13% 3 1	500
	21st to end	Day	32% 21% 30% 11% 4 2	550
April	1st to 10th	Day	35% 23% 24% 12% 5% 1	500
	11th to 20th	Day	27% 25% 27% 13% 7% 1	452
	21st to end	Day	29% 18% 31% 15% 5% 2	460
May	1st to 10th	Day	34% 17% 29% 13% 6% 2	463
	11th to 20th	Day	22% 17% 34% 19% 8% 1	487
	21st to end	Day	18% 13% 27% 27% 11% 4	529
June	1st to 10th	Day	20% 11% 31% 23% 13% 2	490
	11th to 20th	Day	14% 15% 30% 25% 14% 2	490
	21st to end	Day	16% 14% 28% 26% 14% 2	490
July	1st to 10th	Day	14% 8% 29% 30% 14% 4	485
	11th to 20th	Day	12% 6% 29% 32% 17% 2	484
	21st to end	Day	14% 9% 31% 30% 14% 2	532
August	1st to 10th	Day	14% 9% 27% 30% 15% 5%	486
	11th to 20th	Day	14% 9% 28% 28% 16% 6%	479
	21st to end	Day	12% 9% 28% 28% 15% 7%	539
September	1st to 10th	Day	20% 12% 23% 22% 16% 7%	490
	11th to 20th	Day	13% 11% 28% 21% 16% 11%	490
	21st to end	Day	23% 11% 26% 24% 11% 5%	490
October	1st to 10th	Day	30% 9% 24% 18% 15% 4	490
	11th to 20th	Day	18% 18% 29% 24% 10% 2	490
	21st to end	Day	28% 14% 28% 21% 9% 1	443
November	1st to 10th	Day	20% 18% 25% 25% 10% 2	395
	11th to 20th	Day	26% 20% 29% 19% 5% 1	400
	21st to end	Day	25% 21% 29% 20% 4 1	295
December	1st to 10th	Day	24% 27% 31% 14% 5%	200
	11th to 20th	Day	34% 26% 26% 14% 2	200
	21st to end	Day	25% 22% 29% 19% 5%	220
January	1st to 10th	Night	22% 18% 38% 19% 3	800
	11th to 20th	Night	26% 20% 30% 22% 3	800
	21st to end	Night	19% 21% 37% 20% 3	880
February	1st to 10th	Night	24% 19% 34% 22% 2	800
	11th to 20th	Night	25% 20% 38% 17% 1	783
	21st to end	Night	25% 18% 36% 18% 2	660
March	1st to 10th	Night	24% 22% 32% 19% 3	800
	11th to 20th	Night	23% 22% 32% 19% 4	800
	21st to end	Night	23% 21% 34% 17% 5%	880
April	1st to 10th	Night	26% 21% 31% 19% 3	800
	11th to 20th	Night	24% 17% 31% 23% 5%	754
	21st to end	Night	24% 17% 32% 21% 5%	698
May	1st to 10th	Night	25% 18% 30% 22% 5%	570
	11th to 20th	Night	21% 13% 35% 27% 4	390
	21st to end	Night	18% 8% 27% 37% 10% 1	411
June	1st to 10th	Night	17% 6% 30% 34% 12% 1	380
	11th to 20th	Night	16% 7% 29% 31% 16% 1	380
	21st to end	Night	15% 4 25% 44% 12% 1	380
July	1st to 10th	Night	15% 3 21% 40% 20% 1	370
	11th to 20th	Night	14% 4 22% 43% 15% 1	368
	21st to end	Night	13% 5% 23% 42% 17%	416
August	1st to 10th	Night	14% 2 22% 44% 15% 2	434
	11th to 20th	Night	15% 4 19% 40% 20% 2	750
	21st to end	Night	16% 4 20% 36% 21% 2	836
September	1st to 10th	Night	17% 5% 28% 33% 14% 3	760
	11th to 20th	Night	16% 6% 24% 31% 20% 4	760
	21st to end	Night	21% 6% 26% 31% 14% 2	760
October	1st to 10th	Night	24% 9% 26% 26% 13% 1	760
	11th to 20th	Night	19% 11% 29% 31% 9% 1	760
	21st to end	Night	27% 12% 27% 26% 7%	836
November	1st to 10th	Night	19% 11% 31% 29% 9% 1	780
	11th to 20th	Night	22% 16% 32% 22% 7% 1	800
	21st to end	Night	20% 18% 31% 24% 6% 1	800
December	1st to 10th	Night	27% 16% 30% 21% 6%	800
	11th to 20th	Night	25% 16% 32% 24% 4	800
	21st to end	Night	27% 15% 35% 21% 2	880

Page generated at 2025-04-08 09:17:29. Version ac07

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