Carrizo Plain National Monument
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Carrizo Plain National Monument clear sky chart from 2005-11-06 to 2025-04-26.

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	3 3 1 3 3 3 3 3 4 6% 69%	117508
	Night	3 4 1 4 3 3 3 3 5% 6% 65%	120003
Transparency	Day	16% 4 8% 17% 28% 27%	117262
	Night	18% 5% 9% 18% 26% 23%	119839
Seeing	Day	5% 7% 20% 32% 26% 9%	16111
	Night	4 4 12% 36% 36% 8%	25869

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	3 6% 2 5% 3 3 5% 4 6% 7% 57%	3731
	11th to 20th	Day	4 4 1 4 3 4 4 3 5% 7% 63%	4100
	21st to end	Day	6% 7% 2 6% 4 4 5% 4 6% 8% 49%	4510
February	1st to 10th	Day	7% 6% 2 6% 3 3 3 3 5% 7% 54%	1966
	11th to 20th	Day	5% 6% 2 6% 4 4 4 4 7% 8% 51%	1950
	21st to end	Day	6% 6% 2 6% 4 5% 4 4 4 8% 52%	1650
March	1st to 10th	Day	7% 7% 3 7% 5% 5% 5% 4 6% 8% 42%	4518
	11th to 20th	Day	3 5% 2 7% 5% 4 4 4 5% 7% 55%	4955
	21st to end	Day	3 4 2 6% 5% 6% 6% 5% 8% 10% 44%	5833
April	1st to 10th	Day	5% 5% 2 4 4 4 4 4 6% 8% 56%	2400
	11th to 20th	Day	3 4 1 4 3 3 4 3 5% 7% 62%	2369
	21st to end	Day	3 3 1 2 3 2 4 3 5% 7% 68%	2342
May	1st to 10th	Day	2 2 1 2 1 2 2 2 3 5% 79%	3800
	11th to 20th	Day	2 1 1 1 1 2 2 3 5% 81%	4008
	21st to end	Day	2 1 1 1 2 2 2 3 4 83%	4653
June	1st to 10th	Day	2 1 1 2 2 2 3 3 4 7% 74%	2660
	11th to 20th	Day	1 1 1 1 1 1 1 2 3 88%	2660
	21st to end	Day	1 1 1 1 1 1 2 3 89%	2660
July	1st to 10th	Day	1 2 2 92%	4420
	11th to 20th	Day	1 1 1 2 1 1 2 2 2 4 83%	4274
	21st to end	Day	1 1 1 1 1 1 1 2 3 87%	4439
August	1st to 10th	Day	1 1 1 1 1 1 2 4 87%	3783
	11th to 20th	Day	1 1 1 1 1 94%	3724
	21st to end	Day	1 1 1 1 1 1 2 92%	4180
September	1st to 10th	Day	1 1 1 1 1 1 1 1 2 4 87%	2280
	11th to 20th	Day	1 1 2 1 1 1 1 2 3 86%	2228
	21st to end	Day	1 1 1 1 1 1 2 2 4 85%	2090
October	1st to 10th	Day	1 1 1 2 1 1 2 2 4 5% 79%	3318
	11th to 20th	Day	1 2 1 2 2 2 3 2 3 5% 78%	3161
	21st to end	Day	3 3 1 3 2 3 4 3 4 7% 66%	3448
November	1st to 10th	Day	3 4 2 3 3 3 3 2 4 6% 65%	1816
	11th to 20th	Day	3 4 1 4 3 3 4 4 5% 6% 63%	1800
	21st to end	Day	5% 5% 2 5% 4 5% 4 4 6% 6% 55%	1800
December	1st to 10th	Day	3 4 2 5% 4 4 5% 3 5% 7% 58%	2950
	11th to 20th	Day	6% 6% 2 7% 4 4 5% 5% 7% 8% 46%	3028
	21st to end	Day	6% 8% 3 7% 5% 5% 5% 4 7% 10% 39%	4004
January	1st to 10th	Night	4 10% 3 6% 4 4 3 3 5% 7% 52%	6201
	11th to 20th	Night	4 4 2 6% 4 3 3 3 4 6% 60%	5880
	21st to end	Night	7% 8% 2 7% 4 4 4 4 5% 7% 47%	6468
February	1st to 10th	Night	6% 7% 2 6% 4 3 4 3 5% 6% 54%	2431
	11th to 20th	Night	5% 5% 2 5% 4 3 3 5% 6% 8% 54%	2338
	21st to end	Night	4 4 2 6% 4 4 5% 3 5% 6% 56%	1980
March	1st to 10th	Night	5% 6% 3 7% 5% 5% 6% 5% 7% 9% 43%	5376
	11th to 20th	Night	3 5% 2 6% 4 4 4 4 6% 7% 54%	5029
	21st to end	Night	6% 6% 2 6% 5% 4 5% 4 6% 8% 48%	5140
April	1st to 10th	Night	4 3 2 4 3 4 4 4 5% 8% 60%	2000
	11th to 20th	Night	3 3 1 3 3 3 2 2 4 6% 69%	1979
	21st to end	Night	2 2 1 2 1 3 3 3 5% 8% 71%	1954
May	1st to 10th	Night	1 1 1 2 1 1 2 1 3 5% 82%	3180
	11th to 20th	Night	1 1 1 1 1 2 2 5% 6% 81%	2898
	21st to end	Night	1 1 1 1 1 1 1 3 3 87%	2922
June	1st to 10th	Night	1 1 2 2 2 3 2 3 5% 80%	1520
	11th to 20th	Night	1 1 1 1 3 3 89%	1520
	21st to end	Night	1 1 1 1 2 2 92%	1520
July	1st to 10th	Night	1 1 2 3 92%	2540
	11th to 20th	Night	1 1 1 1 1 2 2 3 88%	2687
	21st to end	Night	1 1 1 1 1 1 1 2 3 89%	3123
August	1st to 10th	Night	1 1 1 1 1 1 1 2 2 89%	3166
	11th to 20th	Night	1 1 1 1 2 93%	3126
	21st to end	Night	1 1 1 1 2 94%	3498
September	1st to 10th	Night	1 1 1 1 1 2 1 2 3 87%	1900
	11th to 20th	Night	1 1 2 1 1 2 2 2 4 84%	1950
	21st to end	Night	1 1 1 1 1 2 2 3 4 85%	2090
October	1st to 10th	Night	1 1 1 1 1 1 1 2 4 84%	3645
	11th to 20th	Night	1 1 2 2 2 2 3 4 5% 79%	3777
	21st to end	Night	2 3 1 3 2 2 2 2 4 5% 73%	4121
November	1st to 10th	Night	2 4 1 4 3 3 3 3 4 8% 65%	2481
	11th to 20th	Night	3 4 1 4 3 3 3 4 5% 7% 64%	2600
	21st to end	Night	5% 5% 2 5% 4 3 6% 4 6% 7% 53%	2600
December	1st to 10th	Night	3 3 2 4 3 4 3 4 6% 7% 60%	4240
	11th to 20th	Night	6% 7% 2 7% 5% 6% 6% 5% 8% 9% 40%	5171
	21st to end	Night	6% 10% 3 7% 6% 6% 7% 6% 7% 9% 33%	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	21% 8% 14% 27% 19% 12%	3731
	11th to 20th	Day	19% 7% 11% 16% 18% 29%	4100
	21st to end	Day	28% 8% 11% 14% 20% 19%	4510
February	1st to 10th	Day	29% 4 8% 19% 24% 16%	1966
	11th to 20th	Day	27% 6% 11% 23% 24% 10%	1960
	21st to end	Day	28% 7% 11% 22% 25% 7%	1650
March	1st to 10th	Day	33% 8% 14% 14% 21% 10%	4518
	11th to 20th	Day	24% 7% 14% 30% 18% 8%	4955
	21st to end	Day	25% 11% 16% 27% 17% 3	5833
April	1st to 10th	Day	25% 6% 12% 25% 24% 8%	2400
	11th to 20th	Day	20% 5% 12% 27% 27% 9%	2372
	21st to end	Day	15% 6% 12% 28% 33% 7%	2342
May	1st to 10th	Day	10% 4 8% 22% 34% 22%	3800
	11th to 20th	Day	7% 2 6% 20% 37% 28%	4011
	21st to end	Day	8% 2 6% 24% 47% 13%	4653
June	1st to 10th	Day	9% 5% 9% 21% 35% 20%	2660
	11th to 20th	Day	4 1 6% 15% 38% 35%	2660
	21st to end	Day	4 1 3 7% 34% 51%	2660
July	1st to 10th	Day	2 1 2 4 17% 74%	4351
	11th to 20th	Day	8% 1 4 6% 20% 61%	4199
	21st to end	Day	5% 2 3 14% 29% 47%	4299
August	1st to 10th	Day	5% 1 3 9% 36% 46%	3770
	11th to 20th	Day	2 1 7% 32% 58%	3760
	21st to end	Day	3 1 2 9% 34% 51%	4179
September	1st to 10th	Day	5% 2 4 9% 32% 48%	2280
	11th to 20th	Day	6% 1 4 17% 43% 30%	2228
	21st to end	Day	6% 1 4 15% 42% 32%	2090
October	1st to 10th	Day	8% 2 5% 13% 23% 50%	3318
	11th to 20th	Day	12% 2 5% 20% 39% 23%	3161
	21st to end	Day	18% 3 5% 11% 34% 28%	3448
November	1st to 10th	Day	20% 5% 8% 19% 29% 20%	1816
	11th to 20th	Day	19% 4 10% 20% 27% 20%	1800
	21st to end	Day	28% 5% 8% 15% 23% 21%	1800
December	1st to 10th	Day	24% 4 7% 12% 29% 24%	2950
	11th to 20th	Day	29% 9% 13% 16% 20% 13%	3028
	21st to end	Day	35% 9% 14% 20% 18% 4	4004
January	1st to 10th	Night	28% 7% 11% 25% 20% 9%	6201
	11th to 20th	Night	20% 9% 9% 15% 22% 25%	5880
	21st to end	Night	31% 8% 10% 14% 21% 16%	6468
February	1st to 10th	Night	29% 6% 9% 17% 24% 15%	2431
	11th to 20th	Night	24% 7% 10% 25% 24% 10%	2339
	21st to end	Night	27% 7% 11% 22% 27% 6%	1980
March	1st to 10th	Night	28% 10% 15% 20% 21% 6%	5376
	11th to 20th	Night	23% 9% 14% 32% 15% 7%	5029
	21st to end	Night	27% 12% 16% 26% 16% 2	5140
April	1st to 10th	Night	20% 8% 15% 28% 22% 7%	2000
	11th to 20th	Night	18% 5% 12% 26% 30% 9%	1979
	21st to end	Night	11% 5% 14% 32% 31% 7%	1954
May	1st to 10th	Night	7% 4 8% 27% 32% 23%	3180
	11th to 20th	Night	6% 3 6% 23% 38% 24%	2899
	21st to end	Night	5% 2 9% 26% 44% 14%	2922
June	1st to 10th	Night	8% 4 10% 22% 36% 21%	1520
	11th to 20th	Night	3 2 6% 16% 39% 35%	1520
	21st to end	Night	3 1 3 7% 35% 52%	1520
July	1st to 10th	Night	2 1 2 5% 17% 73%	2500
	11th to 20th	Night	3 1 3 9% 17% 67%	2639
	21st to end	Night	4 2 3 13% 30% 49%	3025
August	1st to 10th	Night	6% 1 2 10% 34% 47%	3156
	11th to 20th	Night	2 1 1 6% 28% 61%	3156
	21st to end	Night	3 1 2 8% 33% 54%	3498
September	1st to 10th	Night	6% 2 3 10% 29% 51%	1900
	11th to 20th	Night	6% 2 3 14% 45% 31%	1950
	21st to end	Night	5% 2 4 17% 41% 31%	2090
October	1st to 10th	Night	7% 2 4 10% 25% 51%	3645
	11th to 20th	Night	10% 2 5% 21% 41% 21%	3777
	21st to end	Night	15% 2 4 15% 36% 27%	4121
November	1st to 10th	Night	17% 5% 8% 22% 26% 20%	2481
	11th to 20th	Night	19% 5% 11% 19% 26% 20%	2600
	21st to end	Night	26% 6% 10% 18% 22% 18%	2600
December	1st to 10th	Night	21% 4 7% 16% 33% 19%	4240
	11th to 20th	Night	34% 10% 13% 15% 17% 12%	5171
	21st to end	Night	39% 9% 16% 18% 14% 4	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	13% 12% 28% 34% 11% 3	240
	11th to 20th	Day	10% 12% 28% 33% 13% 4	400
	21st to end	Day	10% 13% 29% 30% 15% 3	440
February	1st to 10th	Day	10% 14% 29% 27% 14% 6%	484
	11th to 20th	Day	10% 15% 28% 32% 13% 3	495
	21st to end	Day	10% 13% 30% 31% 14% 2	414
March	1st to 10th	Day	15% 16% 28% 29% 11% 1	500
	11th to 20th	Day	9% 15% 29% 31% 13% 2	500
	21st to end	Day	9% 17% 33% 29% 10% 3	550
April	1st to 10th	Day	9% 12% 28% 27% 19% 4	500
	11th to 20th	Day	6% 14% 30% 30% 17% 3	492
	21st to end	Day	4 10% 28% 30% 20% 7%	481
May	1st to 10th	Day	7% 9% 31% 29% 19% 6%	463
	11th to 20th	Day	3 8% 23% 35% 23% 7%	488
	21st to end	Day	4 10% 21% 35% 24% 7%	529
June	1st to 10th	Day	2 6% 18% 33% 30% 11%	490
	11th to 20th	Day	1 4 18% 39% 30% 9%	490
	21st to end	Day	1 12% 35% 36% 16%	490
July	1st to 10th	Day	1 6% 33% 41% 19%	486
	11th to 20th	Day	1 4 29% 38% 27%	484
	21st to end	Day	1 1 4 27% 40% 27%	531
August	1st to 10th	Day	2 1 9% 34% 36% 18%	487
	11th to 20th	Day	2 5% 31% 43% 18%	477
	21st to end	Day	1 1 5% 32% 42% 20%	539
September	1st to 10th	Day	1 11% 30% 42% 15%	490
	11th to 20th	Day	2 2 15% 40% 33% 7%	490
	21st to end	Day	1 2 16% 34% 37% 10%	490
October	1st to 10th	Day	1 4 17% 35% 33% 9%	490
	11th to 20th	Day	2 5% 20% 35% 30% 8%	490
	21st to end	Day	3 6% 21% 32% 29% 9%	539
November	1st to 10th	Day	5% 8% 20% 33% 26% 8%	352
	11th to 20th	Day	4 9% 20% 35% 27% 5%	300
	21st to end	Day	7% 9% 20% 35% 24% 4	300
December	1st to 10th	Day	5% 5% 24% 38% 23% 4	300
	11th to 20th	Day	8% 13% 18% 32% 21% 10%	200
	21st to end	Day	14% 11% 30% 29% 11% 5%	220
January	1st to 10th	Night	11% 6% 15% 37% 20% 11%	800
	11th to 20th	Night	6% 4 15% 43% 24% 7%	800
	21st to end	Night	10% 6% 15% 42% 21% 6%	880
February	1st to 10th	Night	8% 8% 17% 39% 22% 7%	800
	11th to 20th	Night	7% 6% 18% 41% 21% 8%	784
	21st to end	Night	7% 8% 18% 44% 19% 4	660
March	1st to 10th	Night	7% 8% 19% 42% 21% 3	800
	11th to 20th	Night	7% 6% 16% 39% 26% 6%	800
	21st to end	Night	7% 8% 18% 39% 25% 3	880
April	1st to 10th	Night	5% 6% 17% 44% 25% 4	800
	11th to 20th	Night	5% 5% 16% 42% 28% 4	791
	21st to end	Night	3 5% 17% 37% 31% 6%	782
May	1st to 10th	Night	2 4 13% 43% 32% 6%	760
	11th to 20th	Night	3 3 13% 38% 39% 5%	599
	21st to end	Night	1 5% 15% 41% 35% 4	507
June	1st to 10th	Night	1 1 8% 35% 50% 4	380
	11th to 20th	Night	7% 37% 52% 4	380
	21st to end	Night	1 4 31% 56% 8%	380
July	1st to 10th	Night	1 16% 74% 9%	370
	11th to 20th	Night	16% 65% 18%	450
	21st to end	Night	1 1 1 13% 64% 21%	626
August	1st to 10th	Night	1 3 23% 60% 13%	756
	11th to 20th	Night	1 20% 63% 15%	752
	21st to end	Night	1 1 20% 63% 15%	836
September	1st to 10th	Night	1 1 2 23% 59% 14%	760
	11th to 20th	Night	1 1 6% 32% 48% 12%	760
	21st to end	Night	1 1 6% 32% 52% 9%	760
October	1st to 10th	Night	1 1 8% 38% 44% 7%	760
	11th to 20th	Night	3 2 8% 39% 39% 10%	760
	21st to end	Night	3 1 10% 39% 37% 10%	836
November	1st to 10th	Night	4 3 13% 38% 32% 10%	780
	11th to 20th	Night	4 2 13% 43% 31% 9%	800
	21st to end	Night	6% 4 16% 40% 25% 9%	800
December	1st to 10th	Night	7% 4 15% 41% 28% 6%	800
	11th to 20th	Night	10% 4 15% 45% 21% 5%	800
	21st to end	Night	8% 8% 18% 39% 19% 7%	880

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