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 2025-02-25.

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	8% 6% 2 4 3 3 3 3 5% 9% 54%	112624
	Night	10% 7% 2 5% 3 3 3 3 5% 8% 53%	114890
Transparency	Day	14% 44% 6% 10% 13% 13%	112385
	Night	17% 44% 6% 10% 12% 12%	114718
Seeing	Day	10% 5% 12% 28% 32% 13%	15828
	Night	12% 5% 11% 26% 33% 14%	25328

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	13% 5% 2 4 3 3 3 3 5% 8% 52%	3989
	11th to 20th	Day	13% 6% 2 5% 3 3 3 3 4 6% 52%	4100
	21st to end	Day	17% 8% 2 6% 4 3 4 3 5% 7% 41%	4510
February	1st to 10th	Day	20% 6% 2 4 4 3 3 3 5% 6% 45%	1800
	11th to 20th	Day	14% 7% 2 5% 4 4 4 4 7% 8% 43%	1858
	21st to end	Day	13% 6% 2 5% 4 3 4 4 5% 7% 47%	1611
March	1st to 10th	Day	15% 10% 3 7% 6% 5% 5% 5% 7% 8% 30%	3404
	11th to 20th	Day	11% 4 1 4 3 3 3 3 5% 8% 55%	3490
	21st to end	Day	15% 8% 2 5% 4 4 5% 4 6% 9% 37%	3875
April	1st to 10th	Day	12% 6% 2 4 4 3 4 4 5% 7% 49%	2280
	11th to 20th	Day	8% 5% 2 5% 3 2 3 3 7% 9% 53%	2249
	21st to end	Day	6% 5% 2 5% 4 4 4 4 6% 9% 52%	2280
May	1st to 10th	Day	6% 3 1 2 2 2 2 2 4 7% 69%	3883
	11th to 20th	Day	3 11% 2 7% 3 3 3 3 5% 11% 50%	4091
	21st to end	Day	3 9% 2 4 3 3 3 3 4 8% 58%	4813
June	1st to 10th	Day	5% 6% 2 5% 5% 3 3 4 6% 9% 51%	2660
	11th to 20th	Day	3 6% 2 3 3 3 3 4 6% 9% 59%	2660
	21st to end	Day	3 5% 2 5% 2 3 3 3 5% 10% 60%	2660
July	1st to 10th	Day	1 4 1 3 2 3 3 3 4 8% 68%	4339
	11th to 20th	Day	2 6% 2 4 3 3 3 3 5% 10% 60%	4110
	21st to end	Day	1 5% 1 5% 3 3 3 4 6% 13% 57%	4455
August	1st to 10th	Day	1 4 1 4 3 3 5% 4 7% 12% 55%	4091
	11th to 20th	Day	1 4 2 3 2 2 3 3 4 10% 66%	3799
	21st to end	Day	1 6% 2 5% 3 3 3 3 5% 12% 58%	4180
September	1st to 10th	Day	1 4 1 3 3 3 3 2 6% 8% 65%	2280
	11th to 20th	Day	4 6% 2 5% 3 3 4 4 6% 10% 54%	2280
	21st to end	Day	4 3 1 2 2 2 2 2 4 10% 67%	2012
October	1st to 10th	Day	2 3 1 3 3 3 3 2 4 7% 68%	3180
	11th to 20th	Day	4 5% 1 3 3 3 3 2 4 8% 64%	3161
	21st to end	Day	5% 4 1 4 3 3 3 3 4 9% 61%	3448
November	1st to 10th	Day	8% 4 2 4 3 4 4 4 6% 7% 55%	1954
	11th to 20th	Day	10% 5% 2 4 3 3 3 4 6% 7% 53%	1800
	21st to end	Day	13% 4 1 4 3 3 3 3 3 8% 56%	1670
December	1st to 10th	Day	8% 4 2 5% 3 3 4 3 6% 9% 53%	2620
	11th to 20th	Day	23% 7% 2 5% 3 4 3 3 5% 7% 37%	3028
	21st to end	Day	29% 8% 2 4 3 3 3 3 5% 7% 34%	4004
January	1st to 10th	Night	10% 6% 2 4 3 3 3 3 5% 8% 54%	5956
	11th to 20th	Night	14% 5% 2 4 3 3 4 3 4 6% 52%	5880
	21st to end	Night	15% 7% 2 6% 4 3 3 3 5% 7% 45%	6468
February	1st to 10th	Night	19% 6% 2 4 3 3 3 3 4 5% 49%	2600
	11th to 20th	Night	13% 7% 2 5% 3 2 4 4 7% 8% 45%	2428
	21st to end	Night	12% 7% 2 4 3 3 3 3 6% 6% 51%	1937
March	1st to 10th	Night	17% 11% 3 6% 5% 4 5% 3 6% 6% 34%	3466
	11th to 20th	Night	12% 4 2 4 3 3 2 2 4 8% 57%	3490
	21st to end	Night	15% 11% 2 6% 5% 4 4 3 5% 8% 37%	3777
April	1st to 10th	Night	12% 6% 2 4 5% 4 4 4 5% 8% 47%	1900
	11th to 20th	Night	10% 6% 1 4 3 3 3 3 5% 7% 54%	1879
	21st to end	Night	6% 7% 1 3 2 3 3 3 5% 11% 56%	1900
May	1st to 10th	Night	4 4 1 3 2 2 2 2 4 9% 66%	3090
	11th to 20th	Night	2 17% 4 9% 4 3 3 3 3 10% 42%	2810
	21st to end	Night	3 10% 1 4 2 3 2 2 4 10% 59%	2762
June	1st to 10th	Night	4 5% 3 5% 3 3 4 4 6% 10% 54%	1520
	11th to 20th	Night	2 7% 2 4 3 3 3 3 5% 8% 62%	1520
	21st to end	Night	3 5% 1 3 2 3 4 3 6% 10% 60%	1520
July	1st to 10th	Night	1 6% 1 3 2 3 2 2 3 7% 69%	2619
	11th to 20th	Night	1 8% 2 5% 3 2 2 2 5% 9% 61%	2860
	21st to end	Night	1 8% 2 6% 4 3 5% 4 7% 13% 48%	3109
August	1st to 10th	Night	2 8% 2 6% 4 4 4 3 6% 11% 50%	2848
	11th to 20th	Night	1 4 1 4 2 2 2 2 4 9% 68%	3035
	21st to end	Night	1 8% 2 6% 3 3 3 3 5% 8% 59%	3498
September	1st to 10th	Night	1 6% 2 3 3 3 3 3 4 8% 63%	1900
	11th to 20th	Night	4 7% 2 4 3 3 3 3 4 9% 57%	1900
	21st to end	Night	3 6% 1 4 2 2 2 2 3 8% 67%	2162
October	1st to 10th	Night	2 3 2 4 2 2 2 2 5% 7% 69%	3800
	11th to 20th	Night	4 6% 2 5% 2 2 3 2 5% 7% 61%	3777
	21st to end	Night	6% 4 2 3 3 2 2 2 4 7% 64%	4121
November	1st to 10th	Night	9% 4 2 4 2 3 3 3 5% 7% 59%	2342
	11th to 20th	Night	10% 5% 1 4 3 4 3 3 6% 9% 54%	2600
	21st to end	Night	10% 4 1 4 3 3 4 3 5% 6% 57%	2728
December	1st to 10th	Night	9% 4 1 4 3 3 4 3 5% 6% 58%	4560
	11th to 20th	Night	22% 7% 2 5% 3 3 4 4 7% 8% 34%	5176
	21st to end	Night	29% 8% 2 5% 4 3 3 3 4 5% 34%	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	20% 30% 14% 19% 11% 6%	3989
	11th to 20th	Day	26% 29% 7% 8% 13% 17%	4100
	21st to end	Day	31% 30% 5% 11% 10% 14%	4510
February	1st to 10th	Day	19% 62% 4 6% 5% 3	1800
	11th to 20th	Day	16% 62% 4 7% 7% 3	1867
	21st to end	Day	13% 63% 4 11% 6% 3	1611
March	1st to 10th	Day	32% 49% 6% 5% 8% 1	3404
	11th to 20th	Day	11% 42% 9% 20% 9% 10%	3490
	21st to end	Day	28% 46% 10% 11% 3 1	3875
April	1st to 10th	Day	14% 65% 5% 9% 6% 1	2280
	11th to 20th	Day	9% 67% 6% 11% 7% 1	2252
	21st to end	Day	9% 66% 7% 8% 7% 2	2280
May	1st to 10th	Day	9% 40% 8% 19% 17% 6%	3883
	11th to 20th	Day	7% 48% 11% 14% 14% 5%	4094
	21st to end	Day	12% 42% 7% 18% 19% 2	4814
June	1st to 10th	Day	8% 66% 5% 9% 10% 3	2660
	11th to 20th	Day	6% 65% 4 9% 12% 3	2660
	21st to end	Day	6% 63% 4 6% 9% 12%	2660
July	1st to 10th	Day	5% 35% 3 5% 4 48%	4272
	11th to 20th	Day	7% 36% 4 6% 4 43%	4041
	21st to end	Day	5% 34% 3 9% 17% 31%	4315
August	1st to 10th	Day	10% 37% 4 5% 16% 27%	4076
	11th to 20th	Day	5% 37% 4 6% 24% 25%	3836
	21st to end	Day	8% 36% 5% 7% 22% 21%	4179
September	1st to 10th	Day	5% 60% 5% 6% 12% 12%	2280
	11th to 20th	Day	9% 60% 6% 7% 11% 6%	2280
	21st to end	Day	6% 60% 4 9% 15% 6%	2012
October	1st to 10th	Day	7% 36% 2 5% 16% 33%	3180
	11th to 20th	Day	9% 37% 6% 15% 22% 11%	3161
	21st to end	Day	13% 37% 4 14% 21% 12%	3448
November	1st to 10th	Day	8% 55% 4 13% 14% 5%	1954
	11th to 20th	Day	14% 57% 6% 11% 9% 2	1800
	21st to end	Day	14% 58% 6% 7% 13% 2	1670
December	1st to 10th	Day	17% 37% 4 12% 23% 7%	2620
	11th to 20th	Day	34% 33% 5% 10% 11% 7%	3028
	21st to end	Day	40% 28% 7% 15% 7% 3	4004
January	1st to 10th	Night	19% 30% 15% 18% 14% 4	5956
	11th to 20th	Night	25% 30% 7% 6% 19% 11%	5880
	21st to end	Night	30% 31% 4 7% 12% 15%	6468
February	1st to 10th	Night	20% 61% 4 5% 6% 4	2600
	11th to 20th	Night	15% 62% 5% 8% 7% 3	2430
	21st to end	Night	12% 64% 5% 11% 7% 2	1937
March	1st to 10th	Night	32% 48% 6% 6% 7% 1	3466
	11th to 20th	Night	14% 41% 9% 14% 13% 9%	3490
	21st to end	Night	28% 48% 7% 12% 3 1	3777
April	1st to 10th	Night	12% 66% 4 8% 7% 2	1900
	11th to 20th	Night	11% 66% 5% 11% 5% 2	1879
	21st to end	Night	9% 69% 5% 9% 7% 2	1900
May	1st to 10th	Night	9% 45% 7% 17% 13% 9%	3090
	11th to 20th	Night	10% 62% 6% 12% 6% 6%	2811
	21st to end	Night	11% 46% 9% 16% 17% 2	2762
June	1st to 10th	Night	9% 67% 3 8% 9% 5%	1520
	11th to 20th	Night	8% 65% 5% 7% 10% 5%	1520
	21st to end	Night	4 64% 3 5% 10% 14%	1520
July	1st to 10th	Night	6% 36% 5% 3 5% 46%	2577
	11th to 20th	Night	9% 36% 4 7% 6% 39%	2806
	21st to end	Night	8% 36% 6% 10% 13% 28%	3011
August	1st to 10th	Night	13% 38% 8% 5% 16% 21%	2839
	11th to 20th	Night	5% 37% 2 4 19% 33%	3063
	21st to end	Night	9% 38% 5% 7% 19% 22%	3498
September	1st to 10th	Night	6% 61% 4 5% 12% 11%	1900
	11th to 20th	Night	8% 60% 3 10% 12% 6%	1900
	21st to end	Night	7% 60% 4 9% 11% 9%	2162
October	1st to 10th	Night	6% 37% 2 4 8% 43%	3800
	11th to 20th	Night	10% 37% 7% 15% 19% 12%	3777
	21st to end	Night	13% 36% 4 14% 16% 17%	4121
November	1st to 10th	Night	8% 56% 4 13% 14% 7%	2342
	11th to 20th	Night	13% 58% 6% 11% 9% 3	2600
	21st to end	Night	16% 58% 4 8% 10% 4	2728
December	1st to 10th	Night	16% 36% 4 13% 18% 12%	4560
	11th to 20th	Night	34% 33% 6% 7% 12% 7%	5176
	21st to end	Night	41% 30% 7% 13% 6% 3	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	26% 3 15% 26% 23% 7%	355
	11th to 20th	Day	16% 2 13% 29% 31% 9%	400
	21st to end	Day	14% 2 13% 31% 31% 9%	440
February	1st to 10th	Day	21% 3 16% 25% 24% 12%	400
	11th to 20th	Day	15% 8% 19% 28% 25% 5%	448
	21st to end	Day	10% 7% 18% 33% 27% 6%	399
March	1st to 10th	Day	20% 6% 20% 29% 20% 5%	460
	11th to 20th	Day	21% 3 16% 27% 24% 9%	460
	21st to end	Day	13% 5% 21% 37% 19% 6%	506
April	1st to 10th	Day	13% 6% 18% 36% 20% 7%	460
	11th to 20th	Day	10% 7% 19% 33% 21% 9%	452
	21st to end	Day	8% 5% 23% 31% 21% 12%	460
May	1st to 10th	Day	7% 5% 18% 33% 29% 8%	463
	11th to 20th	Day	8% 5% 17% 29% 28% 13%	488
	21st to end	Day	9% 7% 15% 25% 28% 16%	529
June	1st to 10th	Day	8% 5% 11% 33% 32% 10%	490
	11th to 20th	Day	5% 5% 16% 31% 33% 11%	490
	21st to end	Day	6% 6% 7% 29% 41% 11%	490
July	1st to 10th	Day	8% 6% 5% 21% 42% 19%	486
	11th to 20th	Day	7% 6% 6% 19% 44% 19%	484
	21st to end	Day	4 6% 3 21% 42% 24%	531
August	1st to 10th	Day	6% 7% 5% 26% 42% 13%	487
	11th to 20th	Day	6% 5% 5% 27% 36% 21%	477
	21st to end	Day	5% 7% 3 22% 41% 22%	539
September	1st to 10th	Day	3 3 6% 25% 45% 19%	490
	11th to 20th	Day	7% 6% 7% 30% 34% 16%	490
	21st to end	Day	5% 5% 8% 21% 41% 20%	490
October	1st to 10th	Day	4 5% 10% 25% 35% 21%	490
	11th to 20th	Day	6% 5% 9% 22% 34% 23%	490
	21st to end	Day	8% 4 8% 31% 33% 16%	539
November	1st to 10th	Day	7% 2 14% 26% 33% 17%	490
	11th to 20th	Day	10% 4 11% 29% 33% 12%	300
	21st to end	Day	12% 1 9% 32% 34% 11%	235
December	1st to 10th	Day	16% 4 11% 28% 31% 12%	200
	11th to 20th	Day	14% 4 19% 24% 30% 10%	200
	21st to end	Day	19% 4 18% 30% 22% 7%	220
January	1st to 10th	Night	17% 4 14% 29% 27% 10%	800
	11th to 20th	Night	16% 3 11% 28% 30% 12%	800
	21st to end	Night	16% 4 9% 30% 33% 8%	880
February	1st to 10th	Night	20% 4 14% 26% 26% 9%	800
	11th to 20th	Night	16% 5% 16% 32% 23% 8%	784
	21st to end	Night	13% 6% 18% 32% 26% 5%	646
March	1st to 10th	Night	19% 7% 15% 28% 26% 6%	760
	11th to 20th	Night	17% 4 14% 29% 29% 8%	760
	21st to end	Night	16% 5% 17% 32% 24% 5%	836
April	1st to 10th	Night	13% 6% 18% 33% 25% 7%	760
	11th to 20th	Night	13% 9% 16% 29% 24% 9%	751
	21st to end	Night	9% 5% 17% 32% 23% 14%	760
May	1st to 10th	Night	9% 4 15% 31% 31% 11%	709
	11th to 20th	Night	8% 8% 11% 26% 32% 15%	551
	21st to end	Night	10% 8% 11% 27% 28% 15%	411
June	1st to 10th	Night	7% 4 9% 32% 36% 12%	380
	11th to 20th	Night	6% 4 10% 29% 42% 9%	380
	21st to end	Night	5% 5% 4 22% 47% 16%	380
July	1st to 10th	Night	7% 7% 3 17% 43% 23%	408
	11th to 20th	Night	9% 4 2 14% 42% 30%	552
	21st to end	Night	10% 7% 3 11% 43% 26%	624
August	1st to 10th	Night	8% 8% 2 19% 42% 20%	567
	11th to 20th	Night	6% 5% 2 20% 46% 21%	697
	21st to end	Night	6% 7% 5% 15% 44% 24%	836
September	1st to 10th	Night	6% 4 3 18% 44% 25%	760
	11th to 20th	Night	6% 5% 5% 22% 44% 17%	760
	21st to end	Night	5% 3 8% 19% 42% 23%	760
October	1st to 10th	Night	7% 3 8% 27% 34% 21%	760
	11th to 20th	Night	8% 4 9% 19% 39% 22%	760
	21st to end	Night	10% 4 7% 26% 34% 21%	836
November	1st to 10th	Night	10% 3 12% 26% 33% 17%	780
	11th to 20th	Night	11% 3 9% 29% 36% 12%	800
	21st to end	Night	10% 2 12% 32% 33% 11%	800
December	1st to 10th	Night	15% 4 11% 31% 31% 9%	800
	11th to 20th	Night	21% 4 13% 27% 28% 7%	800
	21st to end	Night	20% 4 19% 30% 22% 5%	880

Page generated at 2025-02-22 03:51:39. Version ac07

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