Cypress Hills Dark-Sky Preserve - CHICO
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Cypress Hills Dark-Sky Preserve - CHICO clear sky chart from 2005-11-06 to 2026-04-17.

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	6% 7% 3 7% 5% 5% 5% 5% 7% 8% 42%	140327
	Night	4 6% 3 7% 6% 6% 6% 5% 7% 9% 41%	139142
Transparency	Day	36% 7% 16% 26% 12% 2	134962
	Night	35% 7% 18% 25% 12% 2	135516
Seeing	Day	11% 13% 31% 28% 15% 3	17403
	Night	9% 12% 33% 31% 13% 2	26839

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	2 9% 4 11% 7% 8% 7% 6% 7% 10% 30%	4124
	11th to 20th	Day	1 3 2 9% 5% 6% 10% 9% 8% 10% 37%	4140
	21st to end	Day	1 4 3 7% 6% 6% 6% 6% 7% 8% 46%	5038
February	1st to 10th	Day	4 10% 3 10% 8% 7% 7% 6% 7% 8% 29%	1890
	11th to 20th	Day	3 9% 4 9% 7% 7% 8% 6% 10% 10% 28%	1845
	21st to end	Day	3 10% 5% 10% 7% 6% 6% 6% 7% 9% 30%	1557
March	1st to 10th	Day	3 6% 2 9% 6% 5% 5% 5% 7% 9% 43%	4848
	11th to 20th	Day	4 7% 3 7% 5% 6% 6% 6% 8% 10% 38%	5110
	21st to end	Day	5% 14% 6% 11% 8% 8% 7% 5% 6% 7% 22%	5607
April	1st to 10th	Day	5% 11% 3 9% 6% 7% 6% 5% 7% 7% 34%	2527
	11th to 20th	Day	9% 12% 5% 11% 7% 5% 5% 4 6% 7% 29%	2646
	21st to end	Day	10% 11% 4 9% 6% 6% 4 4 5% 8% 33%	2600
May	1st to 10th	Day	10% 11% 4 9% 5% 4 4 3 5% 6% 39%	6266
	11th to 20th	Day	11% 10% 4 10% 7% 7% 6% 5% 6% 7% 27%	6337
	21st to end	Day	11% 8% 3 7% 5% 5% 5% 4 6% 7% 39%	7404
June	1st to 10th	Day	13% 7% 3 8% 5% 4 5% 5% 6% 8% 36%	3000
	11th to 20th	Day	15% 8% 3 7% 6% 6% 5% 5% 6% 8% 31%	3000
	21st to end	Day	8% 5% 1 6% 5% 5% 6% 5% 7% 8% 45%	3000
July	1st to 10th	Day	6% 3 2 6% 4 5% 5% 4 6% 9% 52%	6779
	11th to 20th	Day	5% 4 2 6% 4 4 5% 4 7% 8% 51%	6780
	21st to end	Day	5% 3 1 3 3 4 4 4 6% 7% 59%	7369
August	1st to 10th	Day	7% 5% 2 7% 5% 5% 5% 4 7% 8% 44%	5922
	11th to 20th	Day	3 3 1 5% 4 4 6% 5% 8% 9% 52%	5798
	21st to end	Day	8% 3 1 4 3 3 3 3 5% 6% 62%	6468
September	1st to 10th	Day	10% 6% 2 5% 4 3 3 3 6% 7% 52%	2431
	11th to 20th	Day	11% 7% 2 6% 3 4 5% 3 5% 8% 46%	2275
	21st to end	Day	9% 5% 2 5% 3 3 4 4 6% 7% 52%	2189
October	1st to 10th	Day	5% 5% 2 7% 5% 4 4 4 6% 9% 49%	3270
	11th to 20th	Day	3 5% 3 6% 4 4 5% 4 5% 9% 52%	3250
	21st to end	Day	4 7% 3 6% 5% 4 4 5% 6% 7% 49%	3204
November	1st to 10th	Day	7% 12% 4 10% 7% 5% 6% 4 6% 6% 33%	1648
	11th to 20th	Day	3 7% 3 8% 7% 7% 6% 3 7% 9% 39%	1680
	21st to end	Day	4 9% 4 9% 6% 7% 7% 6% 8% 7% 34%	1675
December	1st to 10th	Day	2 8% 3 9% 9% 10% 8% 6% 6% 9% 30%	2360
	11th to 20th	Day	3 9% 4 9% 7% 6% 7% 6% 8% 10% 31%	2715
	21st to end	Day	2 7% 3 8% 6% 7% 6% 5% 8% 8% 42%	3575
January	1st to 10th	Night	2 7% 3 8% 6% 7% 7% 6% 8% 10% 35%	8768
	11th to 20th	Night	1 3 3 8% 6% 7% 10% 7% 8% 9% 37%	8820
	21st to end	Night	1 3 2 6% 6% 8% 9% 8% 10% 10% 38%	9202
February	1st to 10th	Night	4 10% 4 9% 7% 7% 7% 7% 8% 10% 29%	2730
	11th to 20th	Night	2 7% 4 9% 7% 7% 7% 5% 8% 11% 31%	2662
	21st to end	Night	2 9% 3 10% 8% 7% 6% 6% 8% 9% 32%	2249
March	1st to 10th	Night	2 6% 3 7% 6% 7% 7% 6% 8% 11% 37%	5260
	11th to 20th	Night	4 6% 2 7% 5% 5% 6% 5% 8% 10% 42%	5110
	21st to end	Night	6% 15% 5% 13% 8% 8% 7% 4 7% 8% 19%	5610
April	1st to 10th	Night	6% 10% 3 9% 7% 6% 7% 5% 6% 8% 33%	2090
	11th to 20th	Night	8% 8% 4 9% 7% 6% 5% 5% 8% 8% 32%	1835
	21st to end	Night	7% 9% 3 10% 6% 6% 4 5% 7% 7% 36%	1800
May	1st to 10th	Night	11% 9% 3 7% 5% 4 4 3 5% 6% 43%	3700
	11th to 20th	Night	8% 10% 3 9% 6% 7% 6% 6% 7% 9% 30%	3573
	21st to end	Night	10% 7% 2 8% 5% 4 5% 4 6% 8% 41%	3470
June	1st to 10th	Night	13% 6% 2 8% 5% 4 4 4 6% 8% 41%	1400
	11th to 20th	Night	10% 8% 2 7% 5% 5% 6% 4 6% 7% 41%	1400
	21st to end	Night	6% 4 1 5% 3 3 4 4 9% 9% 51%	1400
July	1st to 10th	Night	5% 3 1 5% 4 4 4 3 5% 8% 58%	3180
	11th to 20th	Night	6% 4 2 5% 4 4 5% 4 6% 7% 53%	3180
	21st to end	Night	4 3 1 3 3 5% 5% 4 5% 7% 60%	3468
August	1st to 10th	Night	8% 5% 2 7% 5% 4 4 3 6% 7% 48%	3887
	11th to 20th	Night	3 3 2 5% 3 5% 6% 4 8% 10% 51%	4051
	21st to end	Night	9% 4 2 4 3 3 3 2 4 6% 61%	4509
September	1st to 10th	Night	9% 5% 1 5% 4 4 4 3 5% 6% 54%	1968
	11th to 20th	Night	8% 7% 2 7% 4 5% 4 3 5% 7% 48%	2121
	21st to end	Night	6% 6% 2 6% 4 4 4 3 5% 8% 53%	2211
October	1st to 10th	Night	5% 6% 2 5% 3 4 5% 4 6% 8% 51%	3920
	11th to 20th	Night	5% 5% 2 6% 5% 5% 5% 4 7% 9% 48%	3898
	21st to end	Night	3 5% 3 6% 5% 5% 5% 4 6% 7% 49%	4561
November	1st to 10th	Night	8% 9% 3 8% 6% 6% 7% 5% 6% 8% 34%	2870
	11th to 20th	Night	3 7% 3 8% 7% 7% 8% 6% 8% 8% 37%	2940
	21st to end	Night	3 9% 3 9% 6% 6% 6% 5% 7% 9% 36%	2940
December	1st to 10th	Night	1 6% 3 9% 7% 9% 8% 6% 8% 10% 32%	5040
	11th to 20th	Night	2 7% 4 12% 7% 7% 7% 6% 9% 9% 30%	5696
	21st to end	Night	2 6% 3 7% 5% 5% 6% 5% 8% 8% 46%	7623

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	45% 6% 21% 23% 5% 1	4125
	11th to 20th	Day	32% 14% 18% 19% 12% 6%	4140
	21st to end	Day	31% 11% 23% 26% 9% 1	5038
February	1st to 10th	Day	46% 7% 18% 16% 11% 1	1890
	11th to 20th	Day	43% 8% 17% 22% 8% 3	1854
	21st to end	Day	47% 6% 17% 20% 9% 1	1557
March	1st to 10th	Day	33% 8% 19% 24% 14% 2	4848
	11th to 20th	Day	36% 8% 18% 24% 14%	5110
	21st to end	Day	53% 10% 18% 13% 5% 1	5607
April	1st to 10th	Day	44% 6% 16% 26% 7%	2527
	11th to 20th	Day	50% 5% 13% 24% 7% 1	2649
	21st to end	Day	46% 5% 16% 25% 7% 1	2600
May	1st to 10th	Day	44% 3 12% 26% 11% 4	6266
	11th to 20th	Day	51% 7% 12% 24% 6%	6341
	21st to end	Day	40% 6% 14% 27% 12%	7406
June	1st to 10th	Day	45% 5% 16% 22% 11% 1	3000
	11th to 20th	Day	47% 6% 13% 23% 11% 1	3000
	21st to end	Day	33% 7% 18% 29% 12% 1	3000
July	1st to 10th	Day	26% 7% 15% 24% 22% 5%	6706
	11th to 20th	Day	28% 6% 16% 29% 15% 5%	6699
	21st to end	Day	21% 7% 13% 29% 21% 8%	7156
August	1st to 10th	Day	27% 7% 12% 32% 19% 3	4312
	11th to 20th	Day	25% 6% 15% 37% 14% 1	4197
	21st to end	Day	22% 4 12% 40% 19% 2	4663
September	1st to 10th	Day	31% 3 13% 27% 19% 6%	2431
	11th to 20th	Day	36% 6% 13% 29% 13% 3	2275
	21st to end	Day	30% 4 15% 32% 17% 2	2189
October	1st to 10th	Day	30% 4 15% 33% 14% 3	3270
	11th to 20th	Day	28% 4 20% 32% 14% 2	3250
	21st to end	Day	31% 7% 12% 37% 13%	3204
November	1st to 10th	Day	49% 6% 14% 20% 9% 1	1648
	11th to 20th	Day	37% 7% 22% 24% 9% 1	1680
	21st to end	Day	43% 8% 19% 20% 9% 1	1675
December	1st to 10th	Day	41% 15% 21% 18% 3 1	2360
	11th to 20th	Day	44% 9% 20% 22% 3	2714
	21st to end	Day	37% 7% 12% 26% 13% 5%	3575
January	1st to 10th	Night	38% 7% 20% 23% 10% 1	8769
	11th to 20th	Night	31% 14% 22% 17% 12% 4	8820
	21st to end	Night	30% 13% 23% 23% 9% 2	9202
February	1st to 10th	Night	44% 6% 19% 18% 12% 2	2730
	11th to 20th	Night	41% 6% 18% 20% 13% 2	2663
	21st to end	Night	43% 6% 16% 24% 10% 3	2249
March	1st to 10th	Night	35% 7% 22% 19% 14% 2	5260
	11th to 20th	Night	34% 5% 19% 27% 14% 1	5110
	21st to end	Night	55% 10% 16% 12% 5% 1	5610
April	1st to 10th	Night	45% 5% 16% 24% 9%	2090
	11th to 20th	Night	43% 6% 14% 24% 12% 1	1835
	21st to end	Night	44% 6% 15% 28% 8% 1	1800
May	1st to 10th	Night	39% 3 11% 29% 15% 2	3699
	11th to 20th	Night	45% 6% 15% 26% 8%	3574
	21st to end	Night	38% 4 20% 28% 10%	3470
June	1st to 10th	Night	40% 5% 18% 26% 11% 1	1400
	11th to 20th	Night	40% 5% 14% 25% 15% 2	1400
	21st to end	Night	25% 6% 18% 36% 13% 2	1400
July	1st to 10th	Night	21% 6% 14% 30% 25% 4	3145
	11th to 20th	Night	27% 6% 13% 30% 19% 5%	3138
	21st to end	Night	20% 7% 11% 31% 22% 9%	3369
August	1st to 10th	Night	27% 5% 10% 35% 19% 4	2821
	11th to 20th	Night	27% 6% 16% 34% 15% 2	2928
	21st to end	Night	28% 4 11% 35% 20% 3	3245
September	1st to 10th	Night	30% 4 13% 29% 17% 8%	1968
	11th to 20th	Night	35% 4 13% 31% 13% 4	2121
	21st to end	Night	29% 5% 15% 31% 18% 2	2211
October	1st to 10th	Night	29% 5% 14% 36% 15% 1	3920
	11th to 20th	Night	30% 5% 16% 30% 17% 2	3898
	21st to end	Night	30% 6% 13% 38% 13%	4561
November	1st to 10th	Night	45% 7% 15% 22% 9% 2	2870
	11th to 20th	Night	37% 7% 25% 20% 11%	2940
	21st to end	Night	39% 8% 24% 19% 9% 1	2940
December	1st to 10th	Night	38% 14% 23% 18% 6% 1	5040
	11th to 20th	Night	44% 8% 25% 17% 5%	5697
	21st to end	Night	33% 6% 14% 27% 15% 6%	7623

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	9% 20% 33% 20% 14% 5%	220
	11th to 20th	Day	9% 18% 33% 26% 11% 3	220
	21st to end	Day	4 20% 40% 27% 8% 1	259
February	1st to 10th	Day	12% 20% 37% 24% 7% 1	330
	11th to 20th	Day	7% 16% 37% 26% 12% 2	330
	21st to end	Day	8% 12% 38% 29% 11% 2	273
March	1st to 10th	Day	10% 14% 36% 27% 11% 2	511
	11th to 20th	Day	10% 15% 36% 24% 11% 4	540
	21st to end	Day	12% 15% 32% 24% 13% 4	594
April	1st to 10th	Day	9% 17% 34% 29% 9% 2	540
	11th to 20th	Day	12% 15% 36% 25% 10% 1	517
	21st to end	Day	17% 12% 31% 26% 12% 2	500
May	1st to 10th	Day	13% 11% 23% 29% 19% 5%	668
	11th to 20th	Day	13% 11% 23% 30% 18% 5%	725
	21st to end	Day	17% 9% 23% 26% 19% 6%	789
June	1st to 10th	Day	16% 12% 24% 29% 16% 2	730
	11th to 20th	Day	18% 15% 32% 22% 11% 2	730
	21st to end	Day	13% 7% 29% 27% 21% 4	730
July	1st to 10th	Day	5% 6% 27% 38% 20% 4	721
	11th to 20th	Day	8% 6% 32% 34% 18% 3	718
	21st to end	Day	6% 6% 25% 36% 21% 5%	794
August	1st to 10th	Day	8% 6% 26% 37% 19% 4	593
	11th to 20th	Day	7% 8% 27% 35% 18% 5%	517
	21st to end	Day	7% 9% 27% 33% 19% 5%	583
September	1st to 10th	Day	12% 9% 32% 32% 14% 2	530
	11th to 20th	Day	12% 10% 30% 29% 15% 4	530
	21st to end	Day	14% 14% 34% 25% 9% 3	519
October	1st to 10th	Day	14% 14% 30% 19% 19% 4	330
	11th to 20th	Day	8% 19% 31% 27% 14% 2	330
	21st to end	Day	13% 19% 37% 22% 7% 1	363
November	1st to 10th	Day	18% 18% 35% 20% 8% 1	330
	11th to 20th	Day	9% 24% 39% 20% 7% 1	330
	21st to end	Day	8% 19% 35% 23% 12% 2	327
December	1st to 10th	Day	8% 22% 39% 20% 9% 2	220
	11th to 20th	Day	10% 23% 36% 24% 5% 2	220
	21st to end	Day	8% 15% 30% 33% 11% 3	242
January	1st to 10th	Night	8% 18% 38% 27% 9% 1	1050
	11th to 20th	Night	7% 19% 37% 27% 9% 1	1050
	21st to end	Night	6% 19% 39% 26% 9% 1	1029
February	1st to 10th	Night	9% 14% 32% 29% 13% 2	840
	11th to 20th	Night	5% 13% 43% 28% 10% 1	824
	21st to end	Night	7% 13% 33% 29% 14% 4	692
March	1st to 10th	Night	7% 11% 37% 32% 12% 1	840
	11th to 20th	Night	10% 12% 34% 33% 10% 3	840
	21st to end	Night	12% 12% 33% 27% 13% 2	924
April	1st to 10th	Night	10% 13% 32% 31% 11% 2	652
	11th to 20th	Night	12% 9% 35% 31% 11% 1	611
	21st to end	Night	13% 10% 30% 34% 13% 1	600
May	1st to 10th	Night	13% 9% 23% 34% 20% 2	600
	11th to 20th	Night	10% 8% 26% 35% 19% 3	573
	21st to end	Night	17% 9% 22% 28% 21% 3	433
June	1st to 10th	Night	17% 10% 23% 31% 17% 2	400
	11th to 20th	Night	14% 10% 33% 32% 11%	400
	21st to end	Night	10% 6% 24% 37% 20% 4	400
July	1st to 10th	Night	6% 6% 23% 44% 19% 1	390
	11th to 20th	Night	7% 6% 31% 40% 14% 1	388
	21st to end	Night	5% 5% 20% 44% 24% 2	438
August	1st to 10th	Night	7% 4 23% 42% 21% 2	597
	11th to 20th	Night	9% 3 20% 42% 25% 1	594
	21st to end	Night	11% 6% 22% 39% 20% 1	660
September	1st to 10th	Night	12% 4 26% 39% 16% 3	600
	11th to 20th	Night	12% 7% 25% 36% 18% 2	721
	21st to end	Night	10% 9% 32% 32% 14% 4	800
October	1st to 10th	Night	13% 10% 27% 33% 17% 1	800
	11th to 20th	Night	10% 13% 33% 29% 13% 2	800
	21st to end	Night	9% 18% 36% 28% 8%	913
November	1st to 10th	Night	14% 14% 37% 29% 7%	1025
	11th to 20th	Night	8% 19% 40% 25% 7% 1	1050
	21st to end	Night	7% 14% 42% 30% 7%	1050
December	1st to 10th	Night	7% 16% 38% 27% 11% 2	1050
	11th to 20th	Night	6% 18% 37% 28% 9% 2	1050
	21st to end	Night	9% 15% 37% 28% 9% 2	1155

Page generated at 2026-04-14 00:44:24. Version ac07

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