West Palm Beach
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the West Palm Beach clear sky chart from 2005-11-06 to 2024-11-05.

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% 6% 2 7% 6% 6% 7% 6% 8% 11% 33%	100653
	Night	7% 6% 2 7% 5% 5% 6% 5% 8% 10% 39%	98335
Transparency	Day	20% 52% 12% 11% 5% 1	104337
	Night	20% 51% 12% 11% 5% 1	102777
Seeing	Day	8% 3 15% 28% 29% 17%	16004
	Night	9% 3 15% 29% 31% 13%	26125

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	10% 8% 2 8% 6% 5% 5% 4 6% 7% 39%	2836
	11th to 20th	Day	16% 8% 3 9% 7% 6% 6% 5% 7% 9% 25%	2840
	21st to end	Day	8% 7% 3 10% 7% 6% 6% 5% 6% 7% 35%	3124
February	1st to 10th	Day	10% 6% 3 7% 5% 5% 5% 4 7% 9% 38%	1881
	11th to 20th	Day	7% 4 2 5% 5% 5% 5% 3 6% 9% 48%	1970
	21st to end	Day	7% 5% 3 5% 6% 6% 6% 4 8% 8% 43%	1727
March	1st to 10th	Day	7% 5% 3 8% 7% 7% 8% 7% 9% 10% 29%	3435
	11th to 20th	Day	4 4 1 5% 4 4 5% 5% 8% 10% 51%	3480
	21st to end	Day	10% 5% 2 5% 5% 4 5% 4 7% 10% 43%	3815
April	1st to 10th	Day	5% 4 1 4 4 5% 6% 6% 9% 12% 45%	2090
	11th to 20th	Day	8% 5% 2 7% 5% 5% 6% 6% 9% 10% 38%	2187
	21st to end	Day	6% 4 2 5% 6% 6% 7% 5% 7% 9% 43%	2280
May	1st to 10th	Day	2 2 1 3 3 4 4 4 7% 12% 58%	3765
	11th to 20th	Day	8% 5% 2 7% 6% 7% 7% 6% 8% 12% 32%	3812
	21st to end	Day	6% 5% 2 6% 5% 5% 6% 5% 8% 11% 42%	4476
June	1st to 10th	Day	14% 8% 3 10% 7% 8% 8% 6% 8% 11% 18%	2470
	11th to 20th	Day	8% 7% 4 10% 9% 7% 8% 7% 9% 10% 23%	2470
	21st to end	Day	7% 7% 3 9% 7% 8% 8% 7% 9% 11% 24%	2470
July	1st to 10th	Day	5% 6% 3 7% 7% 6% 7% 6% 9% 12% 32%	4120
	11th to 20th	Day	6% 6% 3 6% 6% 6% 7% 7% 9% 14% 30%	4120
	21st to end	Day	4 5% 2 7% 6% 6% 7% 6% 10% 15% 31%	4466
August	1st to 10th	Day	5% 5% 3 10% 8% 9% 10% 8% 10% 13% 20%	4015
	11th to 20th	Day	3 4 2 7% 6% 7% 8% 7% 10% 15% 31%	3730
	21st to end	Day	5% 4 2 7% 7% 7% 8% 8% 13% 18% 21%	4003
September	1st to 10th	Day	8% 8% 2 8% 7% 8% 8% 7% 10% 13% 20%	2090
	11th to 20th	Day	7% 7% 3 9% 8% 9% 9% 7% 9% 12% 20%	2090
	21st to end	Day	9% 8% 4 12% 8% 7% 8% 7% 9% 10% 19%	2090
October	1st to 10th	Day	8% 8% 4 9% 7% 6% 8% 7% 10% 11% 22%	1974
	11th to 20th	Day	8% 6% 3 9% 7% 7% 6% 6% 9% 11% 29%	1900
	21st to end	Day	10% 6% 3 8% 6% 6% 6% 6% 8% 10% 33%	2090
November	1st to 10th	Day	8% 6% 3 6% 5% 6% 6% 5% 8% 9% 38%	1898
	11th to 20th	Day	12% 7% 2 7% 6% 8% 5% 5% 7% 9% 32%	1900
	21st to end	Day	8% 6% 2 6% 5% 6% 7% 5% 7% 11% 37%	1900
December	1st to 10th	Day	9% 6% 2 7% 6% 5% 5% 5% 7% 9% 38%	1862
	11th to 20th	Day	11% 7% 2 7% 5% 5% 5% 5% 6% 8% 39%	2153
	21st to end	Day	13% 7% 3 8% 6% 6% 6% 6% 7% 10% 29%	3124
January	1st to 10th	Night	9% 6% 2 7% 5% 5% 5% 5% 8% 9% 38%	4109
	11th to 20th	Night	17% 11% 3 8% 6% 5% 5% 4 6% 8% 27%	4120
	21st to end	Night	9% 7% 3 9% 6% 5% 6% 5% 7% 8% 36%	4532
February	1st to 10th	Night	8% 6% 2 6% 5% 4 5% 5% 6% 9% 43%	2296
	11th to 20th	Night	7% 4 2 5% 4 4 4 3 6% 8% 53%	2093
	21st to end	Night	5% 4 2 5% 4 5% 5% 5% 6% 8% 52%	1727
March	1st to 10th	Night	7% 7% 3 9% 7% 7% 6% 5% 6% 7% 36%	3418
	11th to 20th	Night	4 3 1 5% 4 3 5% 4 7% 10% 54%	3480
	21st to end	Night	6% 5% 2 5% 4 4 5% 4 6% 9% 50%	3817
April	1st to 10th	Night	4 3 1 4 4 4 4 4 7% 10% 55%	2090
	11th to 20th	Night	5% 3 2 6% 5% 5% 5% 4 8% 11% 46%	1942
	21st to end	Night	5% 4 1 5% 4 5% 5% 5% 8% 10% 49%	1900
May	1st to 10th	Night	3 3 1 3 3 3 3 3 6% 9% 64%	3130
	11th to 20th	Night	6% 4 2 6% 4 5% 5% 5% 7% 11% 45%	3108
	21st to end	Night	6% 5% 2 5% 4 4 4 4 7% 9% 49%	3079
June	1st to 10th	Night	10% 9% 3 8% 6% 6% 8% 7% 9% 10% 25%	1710
	11th to 20th	Night	7% 8% 2 8% 6% 5% 6% 6% 9% 11% 31%	1710
	21st to end	Night	5% 6% 2 8% 4 7% 7% 6% 8% 13% 32%	1710
July	1st to 10th	Night	5% 5% 3 6% 5% 6% 6% 5% 8% 13% 39%	2840
	11th to 20th	Night	4 5% 2 7% 6% 6% 6% 6% 10% 14% 34%	2840
	21st to end	Night	2 5% 2 7% 5% 5% 6% 5% 8% 13% 41%	3087
August	1st to 10th	Night	4 5% 2 8% 7% 6% 8% 5% 8% 14% 33%	2879
	11th to 20th	Night	2 3 2 6% 5% 5% 6% 6% 9% 15% 42%	3097
	21st to end	Night	4 4 2 8% 7% 7% 8% 7% 12% 15% 25%	3632
September	1st to 10th	Night	7% 5% 3 9% 7% 7% 7% 7% 9% 13% 25%	2090
	11th to 20th	Night	6% 8% 2 10% 7% 7% 6% 5% 9% 12% 27%	2090
	21st to end	Night	8% 7% 3 9% 7% 8% 8% 6% 9% 10% 25%	2090
October	1st to 10th	Night	9% 7% 3 9% 6% 6% 6% 5% 9% 11% 29%	2204
	11th to 20th	Night	9% 6% 2 7% 5% 5% 6% 5% 8% 9% 37%	2280
	21st to end	Night	11% 6% 2 6% 6% 5% 6% 5% 7% 10% 36%	2508
November	1st to 10th	Night	9% 6% 2 6% 5% 5% 5% 4 7% 11% 39%	2280
	11th to 20th	Night	8% 7% 3 7% 5% 6% 7% 5% 8% 9% 36%	2280
	21st to end	Night	9% 7% 3 7% 6% 5% 5% 5% 6% 9% 39%	2280
December	1st to 10th	Night	7% 4 2 6% 5% 5% 5% 4 7% 9% 46%	2313
	11th to 20th	Night	14% 7% 2 6% 5% 4 4 4 5% 8% 41%	3042
	21st to end	Night	10% 8% 3 10% 6% 7% 6% 5% 7% 8% 30%	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	30% 40% 6% 11% 12% 1	2837
	11th to 20th	Day	38% 41% 7% 9% 4	2840
	21st to end	Day	28% 43% 6% 11% 9% 3	3124
February	1st to 10th	Day	13% 67% 7% 9% 4 1	1881
	11th to 20th	Day	8% 65% 4 10% 10% 3	1980
	21st to end	Day	12% 66% 6% 6% 7% 2	1727
March	1st to 10th	Day	28% 53% 10% 6% 3 1	3435
	11th to 20th	Day	11% 45% 15% 24% 5%	3480
	21st to end	Day	19% 45% 9% 16% 8% 3	3815
April	1st to 10th	Day	8% 67% 8% 12% 5% 1	2090
	11th to 20th	Day	11% 68% 6% 7% 7% 1	2187
	21st to end	Day	9% 67% 5% 9% 9% 1	2280
May	1st to 10th	Day	7% 44% 11% 23% 12% 3	3800
	11th to 20th	Day	20% 47% 17% 13% 3	3816
	21st to end	Day	9% 46% 12% 25% 8%	4489
June	1st to 10th	Day	18% 70% 7% 4 1	2470
	11th to 20th	Day	19% 69% 6% 5%	2470
	21st to end	Day	12% 71% 12% 5%	2470
July	1st to 10th	Day	18% 43% 22% 15% 1	4055
	11th to 20th	Day	22% 43% 28% 7%	4051
	21st to end	Day	20% 46% 24% 11%	4324
August	1st to 10th	Day	31% 47% 17% 5%	4002
	11th to 20th	Day	17% 45% 23% 14% 1	3766
	21st to end	Day	22% 48% 26% 4	4003
September	1st to 10th	Day	19% 68% 8% 5%	2090
	11th to 20th	Day	18% 65% 11% 5% 1	2090
	21st to end	Day	19% 66% 7% 6% 2	2090
October	1st to 10th	Day	33% 44% 12% 8% 2	3273
	11th to 20th	Day	26% 40% 12% 11% 10% 1	3140
	21st to end	Day	19% 39% 7% 21% 11% 2	3428
November	1st to 10th	Day	15% 62% 8% 8% 5% 1	1898
	11th to 20th	Day	20% 62% 4 7% 4 2	1900
	21st to end	Day	16% 62% 5% 9% 5% 2	1900
December	1st to 10th	Day	17% 62% 6% 9% 5% 1	1862
	11th to 20th	Day	19% 50% 5% 9% 12% 6%	2150
	21st to end	Day	34% 45% 8% 9% 4 1	3124
January	1st to 10th	Night	29% 42% 8% 13% 7% 1	4109
	11th to 20th	Night	40% 41% 7% 9% 2 1	4120
	21st to end	Night	27% 44% 6% 12% 7% 4	4532
February	1st to 10th	Night	10% 68% 7% 10% 5%	2296
	11th to 20th	Night	8% 65% 4 9% 11% 4	2094
	21st to end	Night	11% 67% 5% 7% 7% 3	1727
March	1st to 10th	Night	33% 49% 8% 7% 3 1	3418
	11th to 20th	Night	12% 46% 18% 19% 5% 1	3480
	21st to end	Night	17% 46% 10% 12% 13% 2	3817
April	1st to 10th	Night	7% 67% 8% 13% 4 1	2090
	11th to 20th	Night	9% 68% 6% 8% 8% 1	1942
	21st to end	Night	7% 67% 7% 11% 6% 1	1900
May	1st to 10th	Night	8% 44% 14% 24% 8% 3	3160
	11th to 20th	Night	15% 46% 16% 19% 4	3109
	21st to end	Night	9% 45% 12% 26% 8%	3087
June	1st to 10th	Night	15% 68% 9% 6% 1	1710
	11th to 20th	Night	17% 69% 8% 6%	1710
	21st to end	Night	10% 69% 14% 6%	1710
July	1st to 10th	Night	17% 42% 25% 15% 1	2795
	11th to 20th	Night	20% 43% 31% 5%	2786
	21st to end	Night	19% 43% 26% 11% 1	2988
August	1st to 10th	Night	26% 44% 21% 7% 1	2868
	11th to 20th	Night	15% 43% 23% 17% 2	3127
	21st to end	Night	25% 47% 23% 4	3632
September	1st to 10th	Night	18% 68% 9% 5%	2090
	11th to 20th	Night	16% 67% 11% 5% 1	2090
	21st to end	Night	16% 65% 9% 7% 3	2090
October	1st to 10th	Night	37% 43% 10% 8% 2	3672
	11th to 20th	Night	27% 40% 8% 13% 10% 1	3779
	21st to end	Night	21% 40% 8% 20% 9% 3	4120
November	1st to 10th	Night	16% 61% 8% 9% 5% 2	2280
	11th to 20th	Night	18% 64% 5% 7% 4 2	2280
	21st to end	Night	17% 62% 4 8% 6% 2	2280
December	1st to 10th	Night	14% 62% 6% 11% 7%	2313
	11th to 20th	Night	18% 52% 6% 9% 9% 7%	3044
	21st to end	Night	34% 45% 8% 7% 4 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	10% 6% 33% 37% 12% 1	270
	11th to 20th	Day	10% 8% 33% 31% 16% 2	270
	21st to end	Day	11% 10% 34% 36% 8%	297
February	1st to 10th	Day	6% 7% 28% 40% 16% 3	270
	11th to 20th	Day	8% 4 24% 41% 18% 4	393
	21st to end	Day	8% 4 21% 37% 27% 1	382
March	1st to 10th	Day	4 5% 32% 38% 18% 2	460
	11th to 20th	Day	6% 6% 25% 38% 22% 2	460
	21st to end	Day	4 4 27% 39% 23% 3	506
April	1st to 10th	Day	4 4 31% 40% 17% 4	460
	11th to 20th	Day	8% 5% 22% 40% 21% 4	452
	21st to end	Day	6% 2 17% 42% 30% 4	460
May	1st to 10th	Day	3 1 14% 38% 33% 10%	463
	11th to 20th	Day	10% 2 15% 34% 28% 11%	487
	21st to end	Day	11% 1 9% 21% 39% 19%	529
June	1st to 10th	Day	12% 2 7% 23% 37% 19%	490
	11th to 20th	Day	10% 2 6% 17% 34% 31%	490
	21st to end	Day	4 3 12% 36% 44%	490
July	1st to 10th	Day	4 1 4 13% 33% 46%	485
	11th to 20th	Day	6% 3 10% 39% 43%	484
	21st to end	Day	5% 1 4 13% 37% 40%	532
August	1st to 10th	Day	6% 2 5% 14% 34% 39%	486
	11th to 20th	Day	4 3 9% 39% 44%	479
	21st to end	Day	10% 4 17% 36% 32%	539
September	1st to 10th	Day	8% 1 5% 13% 35% 38%	490
	11th to 20th	Day	5% 1 7% 16% 34% 37%	490
	21st to end	Day	11% 1 9% 19% 33% 26%	490
October	1st to 10th	Day	13% 2 9% 31% 33% 11%	490
	11th to 20th	Day	10% 5% 15% 28% 32% 9%	490
	21st to end	Day	9% 4 19% 33% 28% 8%	539
November	1st to 10th	Day	10% 5% 18% 33% 28% 6%	472
	11th to 20th	Day	12% 3 23% 34% 22% 5%	460
	21st to end	Day	7% 3 23% 39% 25% 3	460
December	1st to 10th	Day	11% 3 21% 37% 26% 3	422
	11th to 20th	Day	9% 5% 21% 39% 23% 3	270
	21st to end	Day	9% 6% 22% 41% 21% 2	297
January	1st to 10th	Night	10% 5% 24% 36% 23% 2	760
	11th to 20th	Night	11% 6% 26% 35% 20% 2	760
	21st to end	Night	9% 7% 32% 39% 13% 1	836
February	1st to 10th	Night	11% 6% 23% 38% 21% 1	760
	11th to 20th	Night	8% 6% 26% 39% 20% 1	743
	21st to end	Night	8% 4 22% 42% 23% 1	628
March	1st to 10th	Night	5% 4 32% 39% 18% 1	760
	11th to 20th	Night	6% 3 24% 41% 24% 2	760
	21st to end	Night	6% 4 23% 45% 21% 1	836
April	1st to 10th	Night	5% 3 20% 46% 24% 2	760
	11th to 20th	Night	6% 5% 20% 42% 25% 2	751
	21st to end	Night	6% 2 19% 46% 25% 1	760
May	1st to 10th	Night	5% 2 13% 43% 35% 3	760
	11th to 20th	Night	10% 2 13% 39% 32% 5%	740
	21st to end	Night	8% 2 9% 23% 46% 12%	617
June	1st to 10th	Night	13% 2 6% 21% 43% 16%	570
	11th to 20th	Night	8% 2 5% 14% 42% 28%	570
	21st to end	Night	7% 1 5% 9% 39% 39%	570
July	1st to 10th	Night	5% 1 4 8% 42% 40%	555
	11th to 20th	Night	6% 1 2 7% 40% 45%	552
	21st to end	Night	4 2 9% 40% 43%	624
August	1st to 10th	Night	7% 1 7% 10% 39% 37%	595
	11th to 20th	Night	4 1 3 8% 45% 40%	750
	21st to end	Night	9% 1 6% 15% 38% 31%	836
September	1st to 10th	Night	9% 1 5% 10% 38% 35%	760
	11th to 20th	Night	9% 1 6% 13% 41% 31%	760
	21st to end	Night	13% 1 8% 15% 37% 26%	760
October	1st to 10th	Night	13% 3 7% 26% 39% 12%	760
	11th to 20th	Night	12% 3 10% 28% 37% 10%	760
	21st to end	Night	14% 2 14% 33% 31% 7%	836
November	1st to 10th	Night	11% 5% 21% 30% 30% 4	760
	11th to 20th	Night	11% 2 23% 29% 32% 3	760
	21st to end	Night	10% 4 22% 38% 24% 2	760
December	1st to 10th	Night	7% 4 17% 38% 29% 4	760
	11th to 20th	Night	13% 6% 19% 34% 26% 4	760
	21st to end	Night	9% 7% 21% 32% 28% 3	836

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