Paxton Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Paxton Park clear sky chart from 2005-11-06 to 2024-01-22.

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	13% 6% 3 5% 5% 3 5% 5% 5% 8% 42%	74875
	Night	14% 6% 3 5% 5% 3 4 4 5% 7% 45%	75076
Transparency	Day	40% 6% 12% 23% 16% 3	74582
	Night	38% 6% 10% 23% 18% 4	74891
Seeing	Day	15% 7% 21% 26% 21% 11%	14317
	Night	16% 6% 24% 32% 19% 3	24248

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	20% 7% 4 7% 5% 2 5% 4 4 5% 38%	1517
	11th to 20th	Day	21% 9% 3 4 6% 4 4 4 4 5% 35%	1581
	21st to end	Day	14% 7% 4 8% 6% 4 4 3 4 5% 41%	1791
February	1st to 10th	Day	18% 10% 4 5% 5% 3 3 3 6% 7% 36%	1784
	11th to 20th	Day	18% 10% 4 6% 5% 3 4 4 4 5% 37%	1748
	21st to end	Day	19% 9% 4 8% 6% 3 4 3 4 6% 35%	1480
March	1st to 10th	Day	16% 9% 3 5% 5% 3 4 4 4 6% 42%	1800
	11th to 20th	Day	20% 9% 4 6% 6% 3 5% 3 4 5% 35%	1876
	21st to end	Day	19% 9% 3 6% 5% 3 5% 5% 5% 6% 34%	2375
April	1st to 10th	Day	12% 6% 3 5% 4 3 4 4 5% 8% 46%	2160
	11th to 20th	Day	14% 8% 2 7% 5% 3 4 4 5% 7% 40%	2134
	21st to end	Day	17% 6% 3 6% 4 3 4 4 5% 7% 39%	2160
May	1st to 10th	Day	16% 7% 3 5% 5% 3 5% 5% 5% 9% 37%	2281
	11th to 20th	Day	16% 6% 3 6% 5% 3 5% 5% 4 8% 40%	2301
	21st to end	Day	9% 6% 3 6% 7% 4 6% 6% 8% 10% 37%	2639
June	1st to 10th	Day	8% 5% 2 4 5% 3 6% 5% 8% 9% 45%	2520
	11th to 20th	Day	4 3 2 4 5% 3 6% 6% 7% 10% 50%	2520
	21st to end	Day	6% 4 2 4 5% 4 5% 6% 8% 10% 46%	2520
July	1st to 10th	Day	8% 4 2 5% 7% 4 6% 6% 8% 11% 39%	2520
	11th to 20th	Day	6% 3 2 5% 5% 3 6% 6% 7% 10% 48%	2520
	21st to end	Day	6% 4 2 5% 6% 4 6% 6% 7% 12% 42%	2681
August	1st to 10th	Day	8% 5% 2 5% 5% 3 6% 6% 6% 10% 45%	2148
	11th to 20th	Day	9% 5% 2 5% 6% 3 5% 5% 7% 10% 43%	2125
	21st to end	Day	8% 4 2 5% 5% 4 5% 5% 8% 10% 46%	2376
September	1st to 10th	Day	10% 6% 2 5% 5% 3 5% 5% 6% 8% 47%	2160
	11th to 20th	Day	10% 5% 2 5% 5% 4 4 5% 5% 7% 49%	2048
	21st to end	Day	11% 4 3 3 4 2 4 5% 4 7% 53%	1980
October	1st to 10th	Day	10% 4 2 4 4 2 4 4 4 6% 57%	1957
	11th to 20th	Day	14% 5% 2 5% 5% 2 3 3 4 6% 51%	1800
	21st to end	Day	20% 6% 2 3 4 2 3 4 4 5% 46%	1889
November	1st to 10th	Day	10% 4 3 4 3 2 4 4 5% 6% 53%	1672
	11th to 20th	Day	15% 7% 2 5% 4 2 3 4 5% 5% 49%	1710
	21st to end	Day	18% 9% 2 5% 4 2 4 4 4 6% 42%	1710
December	1st to 10th	Day	18% 9% 2 5% 5% 2 4 5% 4 6% 40%	1691
	11th to 20th	Day	16% 8% 3 7% 6% 3 5% 5% 5% 6% 36%	1918
	21st to end	Day	20% 13% 4 6% 6% 3 4 4 3 5% 31%	2783
January	1st to 10th	Night	19% 8% 3 6% 4 3 4 4 5% 6% 40%	2648
	11th to 20th	Night	19% 9% 5% 7% 5% 2 4 4 4 6% 34%	2594
	21st to end	Night	17% 7% 3 5% 5% 2 3 5% 5% 6% 42%	2600
February	1st to 10th	Night	21% 10% 4 7% 5% 3 4 4 4 5% 35%	2174
	11th to 20th	Night	18% 7% 4 7% 5% 3 4 3 4 6% 40%	2098
	21st to end	Night	19% 9% 3 7% 5% 3 4 5% 4 5% 37%	1776
March	1st to 10th	Night	17% 8% 3 5% 4 3 4 4 4 5% 43%	2160
	11th to 20th	Night	18% 9% 4 5% 4 3 3 4 4 5% 40%	2098
	21st to end	Night	18% 9% 4 6% 6% 3 4 4 5% 6% 35%	1980
April	1st to 10th	Night	12% 4 2 4 4 3 4 4 5% 8% 49%	1800
	11th to 20th	Night	15% 6% 2 5% 4 3 3 5% 4 8% 46%	1775
	21st to end	Night	17% 7% 2 5% 4 3 3 5% 6% 7% 41%	1800
May	1st to 10th	Night	15% 6% 3 5% 4 3 4 5% 5% 8% 43%	1679
	11th to 20th	Night	13% 6% 3 5% 6% 3 4 5% 6% 8% 41%	1592
	21st to end	Night	6% 4 2 6% 5% 3 6% 5% 7% 12% 44%	1632
June	1st to 10th	Night	9% 5% 2 5% 4 2 5% 5% 6% 9% 48%	1440
	11th to 20th	Night	4 3 1 4 4 3 5% 5% 7% 10% 54%	1440
	21st to end	Night	3 2 2 4 4 3 5% 6% 8% 13% 51%	1440
July	1st to 10th	Night	7% 3 1 4 5% 3 5% 8% 7% 9% 47%	1440
	11th to 20th	Night	7% 4 2 5% 4 2 5% 4 5% 12% 52%	1440
	21st to end	Night	6% 4 2 5% 4 3 4 4 7% 10% 52%	1630
August	1st to 10th	Night	5% 3 2 4 5% 3 5% 6% 6% 10% 51%	1790
	11th to 20th	Night	6% 5% 1 3 5% 2 4 5% 6% 10% 52%	1776
	21st to end	Night	7% 5% 2 3 4 3 4 5% 7% 9% 51%	1980
September	1st to 10th	Night	9% 5% 2 5% 4 2 3 4 4 6% 55%	1800
	11th to 20th	Night	8% 5% 3 5% 4 3 4 5% 4 7% 54%	1893
	21st to end	Night	10% 4 2 4 4 3 3 3 4 7% 56%	1980
October	1st to 10th	Night	7% 4 2 4 5% 2 3 3 4 6% 59%	2000
	11th to 20th	Night	14% 4 2 4 4 3 3 3 4 5% 53%	2160
	21st to end	Night	19% 6% 2 5% 4 3 3 4 4 5% 46%	2466
November	1st to 10th	Night	12% 5% 2 5% 3 2 3 3 4 7% 56%	2406
	11th to 20th	Night	14% 5% 3 4 4 2 3 4 4 6% 51%	2470
	21st to end	Night	17% 6% 3 4 4 2 3 3 4 5% 49%	2470
December	1st to 10th	Night	19% 8% 2 5% 5% 2 4 4 5% 5% 39%	2486
	11th to 20th	Night	17% 8% 3 5% 5% 3 4 4 4 5% 43%	3279
	21st to end	Night	18% 11% 4 7% 6% 3 5% 5% 4 5% 31%	4884

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	49% 5% 8% 26% 10% 3	1518
	11th to 20th	Day	50% 5% 10% 23% 11% 1	1581
	21st to end	Day	45% 4 12% 25% 12% 2	1791
February	1st to 10th	Day	49% 4 9% 23% 13% 2	1784
	11th to 20th	Day	50% 4 10% 21% 11% 4	1758
	21st to end	Day	51% 4 9% 18% 12% 6%	1480
March	1st to 10th	Day	45% 4 8% 23% 17% 4	1800
	11th to 20th	Day	52% 5% 10% 19% 11% 3	1876
	21st to end	Day	50% 6% 12% 20% 12% 1	2375
April	1st to 10th	Day	37% 6% 11% 26% 18% 2	2160
	11th to 20th	Day	43% 5% 9% 22% 18% 3	2134
	21st to end	Day	44% 6% 10% 25% 14% 2	2160
May	1st to 10th	Day	43% 8% 12% 24% 11% 1	2281
	11th to 20th	Day	43% 8% 12% 20% 15% 1	2305
	21st to end	Day	39% 10% 16% 21% 11% 2	2639
June	1st to 10th	Day	32% 9% 14% 23% 21% 2	2520
	11th to 20th	Day	27% 8% 14% 27% 21% 3	2520
	21st to end	Day	30% 10% 15% 23% 16% 5%	2520
July	1st to 10th	Day	36% 9% 16% 22% 13% 5%	2451
	11th to 20th	Day	30% 8% 16% 25% 16% 4	2445
	21st to end	Day	32% 9% 16% 28% 13% 2	2532
August	1st to 10th	Day	33% 8% 17% 27% 14% 1	2136
	11th to 20th	Day	35% 9% 14% 25% 15% 1	2125
	21st to end	Day	30% 7% 16% 25% 16% 5%	2376
September	1st to 10th	Day	35% 7% 10% 25% 19% 3	2160
	11th to 20th	Day	34% 6% 9% 24% 24% 3	2048
	21st to end	Day	32% 5% 8% 25% 25% 6%	1980
October	1st to 10th	Day	29% 5% 11% 24% 26% 6%	1957
	11th to 20th	Day	36% 3 7% 24% 22% 8%	1800
	21st to end	Day	40% 4 7% 24% 19% 4	1889
November	1st to 10th	Day	32% 5% 9% 25% 24% 6%	1672
	11th to 20th	Day	38% 4 7% 22% 23% 5%	1710
	21st to end	Day	44% 3 7% 25% 17% 4	1710
December	1st to 10th	Day	46% 4 11% 24% 14% 2	1691
	11th to 20th	Day	46% 6% 9% 24% 13% 2	1915
	21st to end	Day	54% 6% 12% 17% 11% 1	2783
January	1st to 10th	Night	46% 4 9% 23% 16% 2	2648
	11th to 20th	Night	51% 6% 9% 20% 14% 1	2594
	21st to end	Night	43% 5% 11% 26% 15% 2	2600
February	1st to 10th	Night	54% 4 8% 20% 13% 1	2174
	11th to 20th	Night	47% 4 7% 23% 16% 3	2099
	21st to end	Night	50% 5% 9% 16% 15% 4	1776
March	1st to 10th	Night	44% 5% 8% 17% 21% 6%	2160
	11th to 20th	Night	47% 5% 10% 20% 14% 3	2098
	21st to end	Night	49% 6% 10% 21% 12% 2	1980
April	1st to 10th	Night	33% 5% 12% 26% 20% 4	1800
	11th to 20th	Night	37% 5% 10% 22% 21% 6%	1775
	21st to end	Night	41% 6% 10% 23% 18% 2	1800
May	1st to 10th	Night	39% 7% 11% 23% 18% 2	1679
	11th to 20th	Night	40% 6% 13% 23% 15% 2	1593
	21st to end	Night	31% 10% 15% 25% 16% 3	1633
June	1st to 10th	Night	32% 8% 13% 22% 23% 2	1440
	11th to 20th	Night	23% 8% 16% 27% 21% 5%	1440
	21st to end	Night	21% 10% 18% 26% 18% 7%	1440
July	1st to 10th	Night	30% 10% 15% 24% 17% 4	1400
	11th to 20th	Night	26% 7% 18% 25% 17% 6%	1392
	21st to end	Night	26% 9% 15% 33% 17% 1	1540
August	1st to 10th	Night	26% 9% 17% 28% 18% 1	1778
	11th to 20th	Night	26% 8% 16% 26% 20% 3	1776
	21st to end	Night	28% 8% 15% 25% 19% 5%	1980
September	1st to 10th	Night	30% 6% 9% 30% 20% 5%	1800
	11th to 20th	Night	30% 6% 8% 27% 24% 5%	1893
	21st to end	Night	28% 4 10% 26% 24% 7%	1980
October	1st to 10th	Night	27% 5% 8% 23% 30% 7%	2000
	11th to 20th	Night	34% 4 7% 22% 26% 8%	2160
	21st to end	Night	41% 4 6% 22% 20% 6%	2466
November	1st to 10th	Night	30% 3 8% 26% 26% 6%	2406
	11th to 20th	Night	35% 3 7% 24% 23% 9%	2470
	21st to end	Night	39% 4 7% 24% 23% 3	2470
December	1st to 10th	Night	47% 5% 10% 22% 14% 2	2486
	11th to 20th	Night	43% 5% 9% 22% 19% 2	3281
	21st to end	Night	52% 7% 9% 17% 11% 3	4884

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	27% 12% 33% 21% 6% 1	270
	11th to 20th	Day	29% 15% 33% 20% 3 1	270
	21st to end	Day	18% 14% 45% 18% 5%	267
February	1st to 10th	Day	28% 13% 36% 19% 3 1	240
	11th to 20th	Day	28% 19% 37% 15% 3	240
	21st to end	Day	29% 13% 34% 17% 6% 1	198
March	1st to 10th	Day	22% 12% 40% 20% 6%	240
	11th to 20th	Day	26% 15% 35% 19% 5% 1	240
	21st to end	Day	23% 15% 30% 22% 8% 1	461
April	1st to 10th	Day	15% 11% 33% 28% 12% 1	420
	11th to 20th	Day	19% 11% 27% 27% 14% 2	412
	21st to end	Day	20% 9% 30% 27% 10% 4	420
May	1st to 10th	Day	17% 13% 26% 29% 12% 4	423
	11th to 20th	Day	19% 6% 18% 29% 19% 9%	447
	21st to end	Day	12% 2 19% 29% 24% 14%	593
June	1st to 10th	Day	10% 5% 14% 26% 28% 17%	630
	11th to 20th	Day	5% 16% 33% 32% 13%	630
	21st to end	Day	7% 1 15% 35% 26% 15%	630
July	1st to 10th	Day	9% 3 9% 25% 27% 27%	621
	11th to 20th	Day	6% 3 9% 25% 39% 19%	618
	21st to end	Day	6% 2 10% 28% 34% 20%	676
August	1st to 10th	Day	10% 1 8% 27% 33% 20%	446
	11th to 20th	Day	12% 2 9% 24% 36% 17%	439
	21st to end	Day	10% 1 7% 22% 36% 25%	495
September	1st to 10th	Day	9% 4 8% 21% 37% 21%	450
	11th to 20th	Day	10% 2 7% 24% 34% 23%	450
	21st to end	Day	13% 5% 16% 25% 27% 14%	450
October	1st to 10th	Day	10% 3 16% 34% 28% 9%	427
	11th to 20th	Day	15% 9% 31% 27% 13% 4	270
	21st to end	Day	26% 12% 24% 25% 11% 3	297
November	1st to 10th	Day	16% 6% 28% 29% 14% 7%	270
	11th to 20th	Day	12% 12% 32% 28% 14% 2	270
	21st to end	Day	23% 12% 24% 28% 11% 2	270
December	1st to 10th	Day	20% 13% 32% 20% 13% 3	270
	11th to 20th	Day	23% 13% 27% 24% 12%	270
	21st to end	Day	27% 14% 35% 20% 3 1	297
January	1st to 10th	Night	24% 10% 31% 29% 6%	950
	11th to 20th	Night	24% 13% 35% 23% 5%	950
	21st to end	Night	20% 8% 39% 30% 2	1000
February	1st to 10th	Night	26% 10% 34% 28% 3	734
	11th to 20th	Night	22% 11% 39% 25% 3	703
	21st to end	Night	23% 14% 35% 25% 2	592
March	1st to 10th	Night	21% 11% 31% 33% 5%	720
	11th to 20th	Night	22% 8% 34% 28% 8%	658
	21st to end	Night	22% 10% 26% 34% 8% 1	594
April	1st to 10th	Night	14% 8% 35% 34% 9% 1	540
	11th to 20th	Night	17% 9% 27% 33% 13% 1	533
	21st to end	Night	19% 4 31% 33% 12% 1	540
May	1st to 10th	Night	17% 5% 27% 34% 15% 2	540
	11th to 20th	Night	15% 5% 17% 39% 23% 2	531
	21st to end	Night	7% 2 14% 41% 32% 4	584
June	1st to 10th	Night	11% 3 13% 37% 32% 4	540
	11th to 20th	Night	5% 1 9% 44% 39% 2	540
	21st to end	Night	4 1 12% 43% 35% 5%	540
July	1st to 10th	Night	7% 2 6% 29% 44% 12%	525
	11th to 20th	Night	7% 2 8% 28% 46% 9%	522
	21st to end	Night	6% 1 9% 31% 42% 10%	591
August	1st to 10th	Night	7% 1 6% 32% 47% 8%	537
	11th to 20th	Night	8% 1 8% 33% 43% 6%	534
	21st to end	Night	8% 1 4 30% 47% 9%	594
September	1st to 10th	Night	11% 1 8% 33% 41% 7%	540
	11th to 20th	Night	9% 1 8% 32% 42% 8%	633
	21st to end	Night	11% 3 15% 35% 31% 6%	720
October	1st to 10th	Night	9% 3 18% 35% 30% 6%	720
	11th to 20th	Night	16% 4 26% 34% 18% 2	720
	21st to end	Night	22% 7% 26% 31% 12% 2	792
November	1st to 10th	Night	13% 6% 25% 39% 16% 1	740
	11th to 20th	Night	15% 8% 32% 31% 13%	760
	21st to end	Night	20% 8% 29% 30% 11% 1	760
December	1st to 10th	Night	23% 9% 29% 30% 8% 1	776
	11th to 20th	Night	23% 6% 29% 33% 8%	950
	21st to end	Night	27% 10% 30% 29% 4	1045

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