Seagrape Drive
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Seagrape Drive clear sky chart from 2005-11-06 to 2024-11-02.

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	7% 5% 2 7% 6% 6% 6% 5% 8% 10% 38%	100604
	Night	7% 5% 2 7% 5% 5% 5% 5% 7% 10% 42%	98305
Transparency	Day	36% 12% 19% 20% 11% 3	100412
	Night	34% 11% 19% 20% 12% 3	98167
Seeing	Day	6% 3 15% 28% 28% 20%	15802
	Night	7% 2 14% 33% 31% 12%	25893

By Month

Percentage Cloud Cover SE (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	9% 8% 3 7% 4 4 4 4 6% 10% 41%	2836
	11th to 20th	Day	15% 7% 3 7% 5% 5% 6% 5% 6% 10% 32%	2840
	21st to end	Day	6% 6% 3 8% 6% 5% 5% 5% 6% 7% 42%	3352
February	1st to 10th	Day	8% 5% 3 6% 4 5% 6% 3 6% 8% 45%	1900
	11th to 20th	Day	6% 3 2 3 3 3 4 4 6% 8% 57%	1872
	21st to end	Day	5% 3 2 4 3 3 5% 4 6% 9% 56%	1727
March	1st to 10th	Day	5% 4 2 6% 5% 6% 6% 6% 8% 11% 40%	3435
	11th to 20th	Day	3 3 1 4 4 5% 4 4 7% 9% 56%	3480
	21st to end	Day	9% 3 1 4 4 4 4 4 5% 7% 54%	3815
April	1st to 10th	Day	4 3 1 4 5% 4 5% 4 6% 11% 53%	2090
	11th to 20th	Day	6% 3 1 5% 4 5% 6% 4 7% 10% 49%	2071
	21st to end	Day	5% 4 2 6% 4 4 4 5% 6% 10% 50%	2280
May	1st to 10th	Day	2 2 1 4 3 4 4 4 6% 9% 61%	3765
	11th to 20th	Day	5% 4 2 5% 4 4 4 5% 7% 11% 50%	4016
	21st to end	Day	5% 4 2 5% 5% 4 5% 4 7% 10% 49%	4476
June	1st to 10th	Day	13% 9% 4 9% 8% 7% 7% 7% 8% 10% 19%	2470
	11th to 20th	Day	8% 7% 3 9% 7% 7% 8% 6% 10% 12% 21%	2470
	21st to end	Day	9% 6% 3 9% 7% 7% 9% 7% 10% 10% 23%	2470
July	1st to 10th	Day	6% 6% 3 8% 9% 9% 10% 7% 9% 11% 23%	4120
	11th to 20th	Day	5% 5% 2 10% 8% 10% 10% 7% 10% 13% 20%	4120
	21st to end	Day	4 5% 2 8% 7% 7% 8% 7% 10% 13% 28%	4466
August	1st to 10th	Day	4 5% 3 11% 9% 9% 8% 7% 10% 12% 22%	4104
	11th to 20th	Day	4 4 2 9% 7% 8% 9% 7% 11% 14% 25%	3550
	21st to end	Day	6% 5% 3 10% 8% 8% 8% 7% 10% 12% 24%	3828
September	1st to 10th	Day	7% 7% 3 10% 7% 8% 8% 7% 10% 12% 23%	2090
	11th to 20th	Day	8% 7% 3 10% 7% 8% 9% 6% 8% 11% 23%	2090
	21st to end	Day	12% 7% 4 10% 7% 7% 7% 7% 9% 8% 22%	2090
October	1st to 10th	Day	8% 7% 3 8% 6% 6% 7% 6% 8% 11% 30%	2075
	11th to 20th	Day	9% 5% 2 7% 6% 5% 7% 6% 8% 10% 34%	1900
	21st to end	Day	9% 5% 2 7% 5% 5% 6% 4 7% 8% 42%	2090
November	1st to 10th	Day	6% 4 1 6% 5% 5% 5% 4 7% 7% 49%	1867
	11th to 20th	Day	9% 4 3 6% 5% 6% 5% 6% 6% 8% 42%	1900
	21st to end	Day	7% 4 2 6% 5% 4 6% 4 7% 9% 47%	1900
December	1st to 10th	Day	7% 4 2 5% 4 4 5% 4 6% 9% 49%	1772
	11th to 20th	Day	8% 5% 2 6% 5% 4 5% 4 6% 9% 47%	2153
	21st to end	Day	10% 6% 2 7% 6% 5% 6% 5% 7% 10% 37%	3124
January	1st to 10th	Night	8% 6% 2 8% 5% 5% 6% 4 6% 10% 40%	4109
	11th to 20th	Night	16% 10% 4 8% 6% 5% 5% 4 6% 7% 29%	4120
	21st to end	Night	6% 6% 3 8% 5% 5% 5% 4 7% 7% 43%	4299
February	1st to 10th	Night	8% 5% 2 6% 4 4 4 4 6% 9% 49%	2280
	11th to 20th	Night	7% 3 1 4 3 3 4 3 5% 8% 57%	2191
	21st to end	Night	4 3 1 4 3 3 4 3 6% 6% 62%	1727
March	1st to 10th	Night	6% 5% 3 8% 5% 6% 5% 5% 7% 7% 42%	3418
	11th to 20th	Night	5% 2 1 4 3 4 4 4 7% 11% 54%	3480
	21st to end	Night	8% 4 2 5% 3 3 4 3 6% 7% 55%	3817
April	1st to 10th	Night	4 3 1 4 3 3 4 4 7% 9% 59%	2090
	11th to 20th	Night	5% 3 1 4 4 4 3 4 6% 10% 56%	2055
	21st to end	Night	6% 4 1 4 4 4 4 4 6% 9% 54%	1900
May	1st to 10th	Night	6% 4 1 4 4 3 3 3 5% 8% 58%	3130
	11th to 20th	Night	4 4 1 4 4 4 4 3 6% 9% 57%	2890
	21st to end	Night	6% 4 2 5% 3 3 4 4 6% 9% 55%	3079
June	1st to 10th	Night	13% 9% 3 8% 6% 5% 5% 5% 6% 9% 29%	1710
	11th to 20th	Night	7% 6% 3 8% 6% 6% 6% 5% 10% 13% 31%	1710
	21st to end	Night	6% 7% 3 7% 6% 6% 6% 7% 9% 13% 30%	1710
July	1st to 10th	Night	5% 7% 2 9% 7% 7% 6% 6% 9% 12% 30%	2840
	11th to 20th	Night	4 6% 3 8% 6% 8% 8% 6% 10% 12% 29%	2840
	21st to end	Night	4 6% 3 8% 6% 6% 8% 7% 10% 12% 30%	3087
August	1st to 10th	Night	4 5% 3 9% 6% 7% 7% 6% 10% 14% 29%	2825
	11th to 20th	Night	4 6% 3 10% 7% 8% 8% 6% 8% 12% 27%	3237
	21st to end	Night	5% 4 2 8% 7% 7% 9% 8% 10% 14% 26%	3828
September	1st to 10th	Night	5% 4 2 7% 6% 6% 7% 6% 11% 14% 32%	2090
	11th to 20th	Night	8% 6% 2 9% 7% 6% 7% 6% 8% 11% 30%	2090
	21st to end	Night	9% 7% 3 9% 8% 6% 7% 6% 7% 9% 28%	2090
October	1st to 10th	Night	8% 6% 3 9% 6% 5% 6% 5% 7% 11% 35%	2104
	11th to 20th	Night	8% 6% 2 7% 5% 4 5% 4 7% 10% 42%	2280
	21st to end	Night	9% 5% 2 6% 5% 5% 5% 4 6% 8% 45%	2508
November	1st to 10th	Night	7% 5% 2 4 3 4 4 4 5% 8% 54%	2234
	11th to 20th	Night	7% 7% 2 6% 5% 4 5% 4 7% 9% 44%	2280
	21st to end	Night	7% 6% 1 6% 5% 4 4 3 6% 8% 49%	2280
December	1st to 10th	Night	6% 4 2 6% 4 4 4 5% 6% 9% 51%	2403
	11th to 20th	Night	9% 5% 2 4 4 4 4 4 5% 9% 51%	3042
	21st to end	Night	8% 7% 3 8% 5% 5% 5% 4 7% 9% 38%	4532

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	36% 7% 14% 23% 15% 5%	2837
	11th to 20th	Day	45% 10% 13% 18% 10% 4	2840
	21st to end	Day	38% 6% 11% 22% 18% 5%	3352
February	1st to 10th	Day	34% 6% 13% 24% 17% 6%	1900
	11th to 20th	Day	21% 6% 14% 26% 23% 10%	1882
	21st to end	Day	22% 8% 14% 21% 27% 9%	1727
March	1st to 10th	Day	31% 11% 18% 23% 15% 3	3435
	11th to 20th	Day	20% 9% 22% 32% 14% 4	3480
	21st to end	Day	26% 6% 12% 29% 19% 9%	3815
April	1st to 10th	Day	22% 8% 19% 30% 16% 5%	2090
	11th to 20th	Day	27% 9% 19% 25% 16% 4	2071
	21st to end	Day	26% 8% 15% 25% 22% 4	2280
May	1st to 10th	Day	15% 9% 15% 36% 22% 3	3800
	11th to 20th	Day	25% 8% 19% 39% 9%	4020
	21st to end	Day	25% 10% 17% 35% 12% 1	4489
June	1st to 10th	Day	53% 14% 18% 13% 2	2470
	11th to 20th	Day	48% 17% 22% 12% 1	2470
	21st to end	Day	49% 18% 22% 9% 1	2470
July	1st to 10th	Day	46% 17% 25% 10% 1	4055
	11th to 20th	Day	48% 18% 29% 6%	4051
	21st to end	Day	40% 18% 31% 10%	4324
August	1st to 10th	Day	49% 16% 25% 9% 2	4091
	11th to 20th	Day	41% 19% 30% 11%	3587
	21st to end	Day	45% 19% 30% 6% 1	3828
September	1st to 10th	Day	46% 20% 24% 10% 1	2090
	11th to 20th	Day	50% 17% 20% 11% 2	2090
	21st to end	Day	53% 15% 14% 12% 4 1	2090
October	1st to 10th	Day	41% 16% 16% 14% 11% 3	2075
	11th to 20th	Day	39% 10% 16% 18% 12% 3	1900
	21st to end	Day	35% 8% 13% 19% 19% 7%	2090
November	1st to 10th	Day	30% 8% 14% 19% 19% 10%	1867
	11th to 20th	Day	35% 9% 12% 21% 15% 8%	1900
	21st to end	Day	29% 8% 16% 20% 22% 5%	1900
December	1st to 10th	Day	30% 7% 14% 24% 21% 4	1772
	11th to 20th	Day	31% 7% 14% 20% 19% 8%	2150
	21st to end	Day	39% 8% 17% 18% 15% 3	3124
January	1st to 10th	Night	37% 8% 13% 23% 16% 3	4109
	11th to 20th	Night	51% 9% 12% 17% 9% 3	4120
	21st to end	Night	37% 7% 11% 22% 19% 5%	4299
February	1st to 10th	Night	31% 6% 13% 25% 20% 5%	2280
	11th to 20th	Night	25% 6% 12% 25% 23% 10%	2192
	21st to end	Night	20% 6% 13% 23% 30% 8%	1727
March	1st to 10th	Night	36% 9% 13% 24% 14% 4	3418
	11th to 20th	Night	20% 10% 23% 29% 15% 3	3480
	21st to end	Night	24% 8% 13% 25% 24% 6%	3817
April	1st to 10th	Night	21% 7% 18% 33% 16% 4	2090
	11th to 20th	Night	23% 8% 17% 27% 21% 4	2055
	21st to end	Night	23% 9% 16% 27% 22% 4	1900
May	1st to 10th	Night	21% 9% 15% 39% 13% 3	3160
	11th to 20th	Night	22% 8% 22% 36% 12%	2891
	21st to end	Night	23% 9% 17% 34% 16% 1	3087
June	1st to 10th	Night	48% 13% 21% 16% 2	1710
	11th to 20th	Night	39% 15% 28% 16% 3	1710
	21st to end	Night	41% 17% 30% 10% 2	1710
July	1st to 10th	Night	42% 16% 31% 11%	2795
	11th to 20th	Night	42% 18% 32% 7%	2786
	21st to end	Night	39% 18% 30% 13% 1	2988
August	1st to 10th	Night	40% 15% 30% 14% 2	2814
	11th to 20th	Night	45% 17% 29% 8%	3266
	21st to end	Night	41% 20% 33% 5% 1	3828
September	1st to 10th	Night	36% 21% 30% 12% 1	2090
	11th to 20th	Night	43% 18% 23% 14% 2	2090
	21st to end	Night	47% 18% 19% 12% 5%	2090
October	1st to 10th	Night	39% 13% 21% 16% 9% 2	2104
	11th to 20th	Night	36% 9% 19% 19% 15% 2	2280
	21st to end	Night	36% 7% 13% 19% 18% 6%	2508
November	1st to 10th	Night	27% 9% 15% 21% 21% 8%	2234
	11th to 20th	Night	35% 8% 11% 24% 16% 6%	2280
	21st to end	Night	31% 8% 13% 20% 23% 5%	2280
December	1st to 10th	Night	28% 8% 16% 27% 18% 4	2403
	11th to 20th	Night	28% 6% 13% 24% 20% 9%	3044
	21st to end	Night	38% 8% 19% 17% 15% 2	4532

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% 7% 29% 37% 17% 2	270
	11th to 20th	Day	11% 9% 30% 35% 14% 1	270
	21st to end	Day	9% 10% 38% 33% 9% 1	297
February	1st to 10th	Day	5% 8% 27% 40% 17% 2	270
	11th to 20th	Day	5% 5% 25% 43% 18% 4	294
	21st to end	Day	3 5% 21% 42% 27% 2	382
March	1st to 10th	Day	4 5% 28% 42% 19% 2	460
	11th to 20th	Day	6% 5% 27% 35% 26% 2	460
	21st to end	Day	4 3 24% 42% 24% 4	506
April	1st to 10th	Day	3 4 29% 40% 19% 5%	460
	11th to 20th	Day	4 4 27% 37% 23% 5%	452
	21st to end	Day	4 2 22% 37% 30% 5%	460
May	1st to 10th	Day	3 1 13% 37% 35% 10%	463
	11th to 20th	Day	9% 2 19% 29% 27% 14%	487
	21st to end	Day	7% 2 6% 28% 33% 24%	529
June	1st to 10th	Day	14% 2 9% 21% 33% 21%	490
	11th to 20th	Day	9% 3 6% 19% 31% 33%	490
	21st to end	Day	6% 2 3 12% 31% 47%	490
July	1st to 10th	Day	4 1 3 9% 31% 53%	485
	11th to 20th	Day	6% 1 2 9% 34% 48%	484
	21st to end	Day	7% 1 3 13% 31% 46%	532
August	1st to 10th	Day	4 1 6% 12% 34% 44%	486
	11th to 20th	Day	4 1 3 9% 36% 47%	479
	21st to end	Day	8% 1 7% 18% 30% 36%	539
September	1st to 10th	Day	6% 1 4 13% 33% 42%	490
	11th to 20th	Day	6% 1 5% 13% 34% 40%	490
	21st to end	Day	9% 3 5% 18% 31% 34%	490
October	1st to 10th	Day	7% 2 12% 30% 36% 13%	490
	11th to 20th	Day	8% 3 11% 33% 31% 13%	490
	21st to end	Day	8% 3 17% 36% 28% 8%	539
November	1st to 10th	Day	7% 3 19% 34% 29% 8%	459
	11th to 20th	Day	8% 5% 23% 32% 25% 7%	460
	21st to end	Day	5% 2 22% 41% 25% 6%	460
December	1st to 10th	Day	7% 5% 21% 37% 26% 4	332
	11th to 20th	Day	8% 6% 23% 35% 21% 7%	270
	21st to end	Day	6% 6% 21% 38% 24% 5%	297
January	1st to 10th	Night	8% 5% 20% 44% 22% 2	760
	11th to 20th	Night	9% 4 25% 43% 19% 1	760
	21st to end	Night	8% 5% 28% 43% 16%	836
February	1st to 10th	Night	8% 4 26% 44% 18%	760
	11th to 20th	Night	7% 4 23% 44% 21% 2	743
	21st to end	Night	4 3 19% 48% 25% 1	628
March	1st to 10th	Night	4 4 25% 47% 19% 1	760
	11th to 20th	Night	7% 2 21% 46% 24% 1	760
	21st to end	Night	5% 4 24% 46% 21% 1	836
April	1st to 10th	Night	4 3 20% 46% 26% 1	760
	11th to 20th	Night	5% 3 19% 50% 22% 1	751
	21st to end	Night	6% 2 20% 44% 27% 1	760
May	1st to 10th	Night	3 1 12% 49% 33% 3	760
	11th to 20th	Night	5% 1 13% 42% 34% 5%	613
	21st to end	Night	8% 2 5% 29% 48% 8%	617
June	1st to 10th	Night	13% 2 7% 20% 45% 13%	570
	11th to 20th	Night	7% 1 4 14% 46% 28%	570
	21st to end	Night	5% 2 3 10% 43% 38%	570
July	1st to 10th	Night	5% 1 2 8% 42% 43%	555
	11th to 20th	Night	4 1 2 7% 41% 45%	552
	21st to end	Night	5% 2 10% 34% 49%	624
August	1st to 10th	Night	6% 2 11% 44% 37%	567
	11th to 20th	Night	4 1 3 8% 43% 42%	688
	21st to end	Night	7% 1 6% 16% 41% 29%	836
September	1st to 10th	Night	6% 1 5% 11% 44% 34%	760
	11th to 20th	Night	8% 2 5% 17% 41% 28%	760
	21st to end	Night	11% 2 7% 19% 39% 22%	760
October	1st to 10th	Night	10% 3 10% 34% 34% 9%	760
	11th to 20th	Night	9% 3 11% 32% 36% 10%	760
	21st to end	Night	11% 2 16% 37% 28% 6%	836
November	1st to 10th	Night	8% 2 22% 38% 28% 3	745
	11th to 20th	Night	8% 2 20% 38% 30% 3	760
	21st to end	Night	9% 3 17% 43% 27% 1	760
December	1st to 10th	Night	6% 2 18% 41% 31% 2	760
	11th to 20th	Night	8% 3 17% 40% 29% 3	760
	21st to end	Night	6% 4 21% 38% 28% 2	836

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