Davenport Beach
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Davenport Beach clear sky chart from 2005-11-06 to 2026-07-01.

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 4 3 3 3 3 5% 9% 55%	146252
	Night	9% 7% 2 5% 3 3 3 3 5% 8% 53%	143599
Transparency	Day	16% 36% 6% 12% 17% 14%	141187
	Night	19% 37% 6% 11% 14% 13%	139652
Seeing	Day	10% 5% 12% 28% 32% 13%	17655
	Night	12% 5% 11% 26% 33% 14%	27046

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	17% 5% 1 4 3 3 3 3 5% 8% 48%	5183
	11th to 20th	Day	10% 4 2 4 3 3 3 3 4 7% 57%	5340
	21st to end	Day	14% 8% 2 6% 4 4 5% 3 6% 8% 40%	5843
February	1st to 10th	Day	19% 6% 2 4 4 3 3 3 5% 6% 46%	1890
	11th to 20th	Day	14% 7% 3 5% 4 3 4 4 7% 7% 41%	1953
	21st to end	Day	13% 6% 2 6% 4 3 4 4 5% 6% 46%	1730
March	1st to 10th	Day	12% 8% 2 6% 5% 5% 6% 5% 7% 9% 34%	5010
	11th to 20th	Day	14% 4 1 4 3 3 3 3 5% 8% 52%	5110
	21st to end	Day	15% 9% 2 5% 4 4 5% 4 6% 10% 36%	5684
April	1st to 10th	Day	12% 6% 2 4 4 3 4 3 5% 7% 50%	2520
	11th to 20th	Day	8% 5% 2 5% 3 3 3 4 7% 9% 51%	2489
	21st to end	Day	6% 5% 2 6% 4 4 4 4 6% 9% 51%	2520
May	1st to 10th	Day	4 4 1 4 3 3 3 3 6% 9% 61%	7205
	11th to 20th	Day	2 6% 1 4 2 2 2 2 5% 9% 63%	7628
	21st to end	Day	3 7% 1 4 3 3 3 3 5% 10% 58%	8992
June	1st to 10th	Day	4 6% 2 5% 5% 3 3 4 6% 10% 52%	2940
	11th to 20th	Day	3 6% 2 3 3 2 3 3 5% 9% 60%	2940
	21st to end	Day	2 5% 1 5% 2 3 3 3 5% 10% 60%	2940
July	1st to 10th	Day	1 4 2 4 3 3 3 3 4 8% 66%	6200
	11th to 20th	Day	1 7% 3 5% 3 3 3 3 5% 12% 55%	5880
	21st to end	Day	1 6% 2 5% 3 3 3 4 6% 13% 54%	6402
August	1st to 10th	Day	1 4 1 4 2 3 4 3 6% 10% 63%	5777
	11th to 20th	Day	3 1 4 3 2 3 2 4 10% 67%	5478
	21st to end	Day	1 5% 2 4 2 3 3 3 4 11% 62%	5984
September	1st to 10th	Day	1 4 1 4 3 3 3 2 6% 9% 64%	2400
	11th to 20th	Day	4 6% 2 5% 3 3 4 4 6% 10% 54%	2400
	21st to end	Day	5% 3 1 3 2 2 2 2 4 9% 66%	2118
October	1st to 10th	Day	2 3 1 3 3 3 3 3 4 7% 68%	3280
	11th to 20th	Day	4 4 1 3 3 3 3 2 4 8% 64%	3261
	21st to end	Day	5% 4 1 4 3 3 3 3 4 9% 61%	3558
November	1st to 10th	Day	8% 3 2 3 3 4 4 3 6% 7% 56%	2054
	11th to 20th	Day	11% 6% 2 5% 3 4 3 3 6% 6% 51%	1890
	21st to end	Day	12% 4 1 4 3 3 3 3 3 7% 58%	1753
December	1st to 10th	Day	8% 4 2 4 3 3 4 3 6% 9% 54%	2700
	11th to 20th	Day	23% 7% 2 5% 4 4 3 3 5% 7% 37%	3108
	21st to end	Day	29% 8% 2 4 3 3 3 3 5% 7% 34%	4092
January	1st to 10th	Night	17% 6% 2 4 2 2 3 3 5% 7% 49%	7719
	11th to 20th	Night	11% 4 1 3 3 3 3 3 5% 7% 56%	7650
	21st to end	Night	14% 7% 2 6% 4 3 3 3 5% 8% 44%	8371
February	1st to 10th	Night	18% 6% 2 4 3 3 3 3 4 5% 50%	2730
	11th to 20th	Night	14% 7% 2 5% 3 3 4 4 7% 8% 43%	2553
	21st to end	Night	12% 7% 2 5% 4 3 3 3 6% 6% 50%	2076
March	1st to 10th	Night	16% 9% 2 6% 4 4 5% 3 6% 7% 37%	5100
	11th to 20th	Night	15% 5% 2 4 3 3 3 2 4 7% 52%	5110
	21st to end	Night	17% 10% 2 5% 4 3 4 3 4 7% 41%	5532
April	1st to 10th	Night	11% 6% 2 4 4 4 4 4 5% 8% 48%	2100
	11th to 20th	Night	10% 6% 2 5% 3 3 3 3 5% 7% 52%	2079
	21st to end	Night	6% 7% 2 4 2 3 3 3 4 10% 55%	2100
May	1st to 10th	Night	4 6% 2 4 3 2 3 2 4 8% 62%	5747
	11th to 20th	Night	1 10% 3 5% 3 3 3 3 4 8% 58%	5244
	21st to end	Night	3 10% 2 5% 3 3 3 3 4 10% 55%	5181
June	1st to 10th	Night	3 5% 3 5% 4 3 4 4 6% 10% 53%	1680
	11th to 20th	Night	2 8% 2 4 3 2 3 3 4 7% 61%	1680
	21st to end	Night	2 5% 1 3 2 3 4 3 6% 10% 61%	1680
July	1st to 10th	Night	1 8% 2 5% 3 3 2 2 3 7% 66%	3747
	11th to 20th	Night	1 12% 5% 10% 4 3 3 2 4 9% 48%	4100
	21st to end	Night	1 8% 2 5% 4 4 5% 4 7% 14% 46%	4472
August	1st to 10th	Night	1 6% 2 5% 4 3 4 3 5% 10% 57%	4035
	11th to 20th	Night	1 3 2 5% 2 2 3 3 5% 9% 65%	4373
	21st to end	Night	1 7% 3 5% 3 3 3 2 4 7% 60%	5015
September	1st to 10th	Night	1 7% 2 3 3 3 3 3 4 8% 62%	2000
	11th to 20th	Night	4 7% 2 4 3 3 3 3 5% 9% 57%	2000
	21st to end	Night	4 6% 1 4 2 2 2 2 3 8% 65%	2276
October	1st to 10th	Night	3 3 2 4 2 2 2 2 5% 7% 68%	3920
	11th to 20th	Night	4 6% 2 5% 2 2 3 2 5% 7% 62%	3897
	21st to end	Night	6% 4 2 3 3 2 3 2 4 7% 64%	4253
November	1st to 10th	Night	9% 4 2 5% 2 3 3 3 5% 7% 59%	2462
	11th to 20th	Night	11% 5% 2 4 3 4 3 3 5% 9% 52%	2730
	21st to end	Night	9% 4 1 4 3 3 4 3 5% 6% 58%	2865
December	1st to 10th	Night	9% 4 1 4 3 3 4 3 5% 6% 59%	4700
	11th to 20th	Night	21% 7% 3 5% 3 3 4 4 7% 8% 35%	5316
	21st to end	Night	29% 8% 2 5% 4 3 3 3 4 5% 34%	7106

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	28% 24% 13% 18% 12% 5%	5184
	11th to 20th	Day	23% 23% 6% 6% 16% 27%	5340
	21st to end	Day	32% 24% 5% 14% 14% 12%	5843
February	1st to 10th	Day	20% 60% 4 7% 5% 5%	1890
	11th to 20th	Day	19% 59% 4 7% 7% 3	1962
	21st to end	Day	15% 59% 6% 10% 6% 3	1730
March	1st to 10th	Day	33% 35% 6% 9% 16% 1	5010
	11th to 20th	Day	21% 30% 11% 22% 8% 8%	5110
	21st to end	Day	32% 34% 10% 16% 7% 1	5684
April	1st to 10th	Day	15% 59% 6% 10% 8% 2	2520
	11th to 20th	Day	12% 61% 6% 11% 8% 3	2492
	21st to end	Day	13% 60% 7% 10% 8% 2	2520
May	1st to 10th	Day	15% 23% 6% 20% 27% 9%	7205
	11th to 20th	Day	7% 27% 9% 18% 29% 11%	7631
	21st to end	Day	12% 24% 7% 20% 31% 6%	8994
June	1st to 10th	Day	8% 60% 5% 10% 13% 4	2940
	11th to 20th	Day	7% 59% 4 9% 14% 7%	2940
	21st to end	Day	6% 57% 4 6% 12% 15%	2940
July	1st to 10th	Day	5% 25% 2 7% 14% 47%	6134
	11th to 20th	Day	7% 25% 3 6% 10% 48%	5811
	21st to end	Day	9% 24% 6% 17% 20% 23%	6217
August	1st to 10th	Day	10% 36% 4 5% 17% 27%	4206
	11th to 20th	Day	5% 36% 4 6% 24% 25%	3959
	21st to end	Day	8% 35% 5% 7% 23% 21%	4311
September	1st to 10th	Day	6% 58% 5% 7% 13% 11%	2400
	11th to 20th	Day	10% 57% 6% 8% 12% 6%	2400
	21st to end	Day	8% 57% 4 10% 15% 6%	2118
October	1st to 10th	Day	8% 35% 3 6% 17% 32%	3280
	11th to 20th	Day	9% 36% 6% 15% 22% 11%	3261
	21st to end	Day	13% 36% 4 14% 21% 12%	3558
November	1st to 10th	Day	8% 53% 5% 13% 16% 5%	2054
	11th to 20th	Day	18% 54% 6% 11% 9% 2	1890
	21st to end	Day	14% 55% 5% 9% 14% 3	1753
December	1st to 10th	Day	17% 36% 4 14% 23% 7%	2700
	11th to 20th	Day	34% 32% 5% 10% 11% 7%	3108
	21st to end	Day	40% 28% 7% 15% 7% 3	4092
January	1st to 10th	Night	29% 25% 13% 15% 15% 3	7719
	11th to 20th	Night	22% 23% 6% 5% 20% 24%	7650
	21st to end	Night	32% 25% 4 10% 16% 14%	8371
February	1st to 10th	Night	20% 58% 4 5% 7% 6%	2730
	11th to 20th	Night	18% 59% 5% 8% 7% 2	2555
	21st to end	Night	14% 60% 5% 11% 7% 3	2076
March	1st to 10th	Night	34% 35% 5% 8% 15% 2	5100
	11th to 20th	Night	24% 30% 9% 16% 13% 8%	5110
	21st to end	Night	31% 33% 8% 17% 9% 2	5532
April	1st to 10th	Night	14% 60% 5% 10% 9% 2	2100
	11th to 20th	Night	14% 60% 5% 12% 6% 3	2079
	21st to end	Night	11% 62% 5% 11% 8% 2	2100
May	1st to 10th	Night	17% 26% 7% 13% 22% 14%	5745
	11th to 20th	Night	10% 34% 6% 17% 19% 15%	5245
	21st to end	Night	15% 26% 10% 15% 26% 8%	5182
June	1st to 10th	Night	10% 60% 3 9% 11% 7%	1680
	11th to 20th	Night	10% 59% 4 6% 11% 10%	1680
	21st to end	Night	5% 58% 3 5% 13% 16%	1680
July	1st to 10th	Night	8% 26% 4 5% 14% 42%	3705
	11th to 20th	Night	16% 26% 5% 11% 7% 35%	4046
	21st to end	Night	11% 26% 10% 13% 19% 22%	4345
August	1st to 10th	Night	12% 37% 8% 5% 16% 22%	2929
	11th to 20th	Night	5% 36% 3 4 19% 33%	3160
	21st to end	Night	9% 37% 5% 7% 20% 22%	3608
September	1st to 10th	Night	7% 58% 4 7% 13% 11%	2000
	11th to 20th	Night	9% 57% 4 11% 13% 7%	2000
	21st to end	Night	9% 57% 4 9% 12% 9%	2276
October	1st to 10th	Night	7% 36% 2 4 9% 42%	3920
	11th to 20th	Night	10% 36% 7% 16% 20% 12%	3897
	21st to end	Night	14% 35% 4 14% 16% 17%	4253
November	1st to 10th	Night	8% 53% 4 13% 14% 7%	2462
	11th to 20th	Night	16% 55% 6% 11% 9% 3	2730
	21st to end	Night	16% 55% 4 10% 11% 5%	2865
December	1st to 10th	Night	16% 35% 4 14% 18% 13%	4700
	11th to 20th	Night	34% 32% 6% 8% 12% 7%	5316
	21st to end	Night	42% 29% 7% 13% 7% 3	7106

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	26% 3 16% 26% 21% 7%	383
	11th to 20th	Day	15% 2 12% 27% 33% 10%	430
	21st to end	Day	14% 2 13% 31% 32% 9%	473
February	1st to 10th	Day	20% 3 15% 26% 25% 11%	430
	11th to 20th	Day	16% 9% 19% 28% 24% 4	483
	21st to end	Day	10% 6% 18% 35% 26% 5%	446
March	1st to 10th	Day	18% 6% 21% 31% 20% 5%	540
	11th to 20th	Day	19% 4 16% 26% 24% 10%	540
	21st to end	Day	12% 5% 19% 36% 21% 6%	594
April	1st to 10th	Day	12% 6% 19% 34% 23% 7%	540
	11th to 20th	Day	10% 7% 19% 32% 23% 9%	532
	21st to end	Day	9% 5% 22% 31% 22% 11%	540
May	1st to 10th	Day	6% 6% 19% 31% 29% 9%	543
	11th to 20th	Day	7% 5% 19% 29% 27% 12%	568
	21st to end	Day	8% 8% 14% 27% 27% 16%	617
June	1st to 10th	Day	8% 5% 12% 32% 33% 10%	570
	11th to 20th	Day	5% 5% 16% 30% 33% 11%	570
	21st to end	Day	5% 6% 9% 27% 40% 12%	570
July	1st to 10th	Day	7% 6% 6% 21% 41% 19%	527
	11th to 20th	Day	6% 6% 5% 19% 43% 20%	524
	21st to end	Day	4 6% 4 21% 43% 23%	575
August	1st to 10th	Day	6% 7% 6% 26% 41% 14%	527
	11th to 20th	Day	5% 6% 4 26% 38% 20%	517
	21st to end	Day	5% 7% 3 21% 42% 21%	583
September	1st to 10th	Day	3 3 6% 25% 45% 18%	530
	11th to 20th	Day	7% 6% 7% 29% 35% 16%	530
	21st to end	Day	7% 5% 8% 22% 40% 19%	530
October	1st to 10th	Day	5% 5% 11% 25% 34% 20%	530
	11th to 20th	Day	6% 5% 10% 22% 34% 24%	530
	21st to end	Day	8% 5% 8% 31% 33% 16%	583
November	1st to 10th	Day	7% 2 13% 25% 35% 17%	530
	11th to 20th	Day	12% 6% 11% 30% 30% 11%	330
	21st to end	Day	11% 1 9% 32% 34% 13%	258
December	1st to 10th	Day	14% 3 10% 28% 31% 14%	220
	11th to 20th	Day	14% 3 17% 24% 30% 12%	220
	21st to end	Day	20% 4 19% 29% 21% 6%	242
January	1st to 10th	Night	18% 5% 14% 28% 26% 9%	840
	11th to 20th	Night	16% 2 11% 27% 32% 13%	840
	21st to end	Night	16% 4 8% 31% 33% 8%	924
February	1st to 10th	Night	20% 4 14% 27% 27% 9%	840
	11th to 20th	Night	17% 6% 17% 31% 22% 8%	824
	21st to end	Night	13% 6% 18% 33% 25% 5%	692
March	1st to 10th	Night	18% 8% 16% 29% 25% 5%	840
	11th to 20th	Night	16% 4 14% 28% 30% 8%	840
	21st to end	Night	16% 5% 16% 32% 25% 6%	924
April	1st to 10th	Night	12% 6% 18% 32% 25% 7%	840
	11th to 20th	Night	12% 9% 17% 29% 25% 8%	831
	21st to end	Night	9% 6% 17% 32% 23% 13%	840
May	1st to 10th	Night	8% 5% 15% 30% 32% 11%	783
	11th to 20th	Night	8% 8% 12% 27% 31% 14%	609
	21st to end	Night	10% 9% 11% 27% 28% 14%	455
June	1st to 10th	Night	6% 5% 9% 32% 35% 13%	420
	11th to 20th	Night	6% 4 10% 29% 41% 9%	420
	21st to end	Night	4 5% 6% 22% 47% 16%	420
July	1st to 10th	Night	7% 7% 3 17% 44% 22%	430
	11th to 20th	Night	9% 4 2 13% 42% 31%	582
	21st to end	Night	10% 7% 4 11% 42% 26%	657
August	1st to 10th	Night	8% 8% 2 19% 42% 21%	597
	11th to 20th	Night	6% 5% 2 20% 46% 21%	734
	21st to end	Night	6% 6% 5% 15% 45% 24%	880
September	1st to 10th	Night	6% 4 3 19% 44% 24%	800
	11th to 20th	Night	6% 5% 6% 22% 44% 17%	800
	21st to end	Night	6% 3 8% 19% 42% 23%	800
October	1st to 10th	Night	7% 4 8% 27% 34% 21%	800
	11th to 20th	Night	7% 4 9% 20% 39% 22%	800
	21st to end	Night	9% 4 7% 26% 34% 21%	880
November	1st to 10th	Night	10% 3 11% 25% 33% 18%	820
	11th to 20th	Night	13% 3 9% 28% 35% 12%	840
	21st to end	Night	9% 2 11% 32% 35% 11%	840
December	1st to 10th	Night	15% 4 10% 31% 32% 8%	840
	11th to 20th	Night	20% 4 13% 28% 28% 7%	840
	21st to end	Night	21% 5% 18% 30% 22% 5%	924

Page generated at 2026-06-27 23:10:43. Version ac07

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