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 2026-05-17.

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	12% 7% 2 7% 4 4 4 4 6% 7% 42%	131669
	Night	14% 7% 2 6% 4 4 4 3 5% 7% 44%	131336
Transparency	Day	39% 6% 11% 24% 17% 3	135287
	Night	38% 5% 10% 24% 19% 4	135784
Seeing	Day	15% 9% 22% 25% 19% 9%	17449
	Night	17% 7% 24% 31% 18% 2	27320

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	14% 8% 4 10% 4 4 4 4 5% 6% 36%	4691
	11th to 20th	Day	11% 7% 3 6% 4 4 4 3 4 5% 50%	4922
	21st to end	Day	18% 9% 3 8% 4 4 4 3 4 5% 38%	5812
February	1st to 10th	Day	17% 11% 3 6% 4 3 3 2 6% 7% 37%	2082
	11th to 20th	Day	18% 10% 4 7% 4 4 4 3 4 5% 38%	2048
	21st to end	Day	17% 8% 4 8% 5% 4 4 2 4 6% 37%	1730
March	1st to 10th	Day	16% 12% 3 7% 4 4 3 3 4 5% 39%	4580
	11th to 20th	Day	12% 8% 3 6% 4 3 3 2 4 6% 51%	4826
	21st to end	Day	12% 7% 3 7% 5% 4 4 3 5% 6% 43%	6098
April	1st to 10th	Day	14% 6% 2 6% 3 4 4 4 6% 8% 44%	2520
	11th to 20th	Day	13% 8% 3 7% 5% 4 4 4 5% 6% 41%	2494
	21st to end	Day	16% 7% 3 6% 4 4 5% 4 5% 8% 39%	2520
May	1st to 10th	Day	16% 10% 3 9% 5% 5% 6% 5% 6% 9% 27%	5848
	11th to 20th	Day	16% 7% 3 7% 5% 5% 6% 4 6% 8% 33%	5939
	21st to end	Day	14% 7% 2 7% 5% 5% 4 4 6% 7% 39%	6723
June	1st to 10th	Day	9% 5% 2 5% 4 5% 5% 4 8% 9% 44%	2800
	11th to 20th	Day	5% 4 2 5% 5% 5% 6% 5% 6% 10% 48%	2800
	21st to end	Day	5% 5% 2 5% 5% 5% 6% 5% 8% 9% 45%	2800
July	1st to 10th	Day	8% 5% 2 6% 5% 5% 5% 4 7% 10% 43%	6360
	11th to 20th	Day	5% 4 2 6% 5% 5% 6% 5% 8% 11% 43%	6360
	21st to end	Day	7% 6% 3 8% 6% 6% 6% 5% 8% 11% 35%	6740
August	1st to 10th	Day	5% 4 1 4 3 4 4 3 6% 10% 55%	3905
	11th to 20th	Day	9% 4 2 6% 5% 4 5% 4 7% 10% 44%	3849
	21st to end	Day	5% 3 1 5% 4 4 4 4 6% 8% 56%	4312
September	1st to 10th	Day	10% 6% 2 5% 4 4 4 4 6% 8% 48%	2400
	11th to 20th	Day	10% 6% 2 5% 4 5% 4 4 5% 7% 49%	2275
	21st to end	Day	13% 5% 2 5% 4 3 4 3 4 7% 50%	2200
October	1st to 10th	Day	9% 4 2 5% 3 3 4 2 4 6% 59%	2173
	11th to 20th	Day	13% 5% 2 5% 4 3 3 2 4 6% 54%	2000
	21st to end	Day	20% 6% 2 4 3 3 3 3 4 5% 47%	2098
November	1st to 10th	Day	11% 6% 2 6% 3 4 4 3 5% 6% 51%	1852
	11th to 20th	Day	14% 8% 2 6% 4 3 3 3 5% 5% 48%	1890
	21st to end	Day	18% 10% 2 6% 3 2 3 3 4 6% 42%	1890
December	1st to 10th	Day	14% 9% 2 6% 3 3 4 3 4 6% 45%	2974
	11th to 20th	Day	15% 9% 3 7% 5% 5% 4 3 5% 5% 39%	3088
	21st to end	Day	23% 13% 3 8% 5% 4 4 3 4 5% 28%	4070
January	1st to 10th	Night	17% 9% 3 8% 3 4 4 3 4 6% 39%	8232
	11th to 20th	Night	13% 8% 3 6% 4 4 4 3 4 5% 46%	8063
	21st to end	Night	19% 9% 4 6% 4 3 4 3 5% 5% 37%	8402
February	1st to 10th	Night	20% 10% 3 8% 4 4 4 3 4 5% 35%	2536
	11th to 20th	Night	19% 8% 3 8% 4 3 3 3 4 5% 39%	2458
	21st to end	Night	17% 9% 3 7% 5% 4 4 4 4 4 40%	2076
March	1st to 10th	Night	19% 10% 4 7% 5% 3 4 3 4 5% 36%	5493
	11th to 20th	Night	12% 6% 2 6% 4 4 4 4 5% 6% 48%	5383
	21st to end	Night	14% 7% 2 7% 5% 4 4 4 5% 7% 40%	5072
April	1st to 10th	Night	13% 5% 2 5% 3 3 4 3 6% 8% 47%	2100
	11th to 20th	Night	14% 6% 2 5% 4 4 4 3 5% 8% 46%	2075
	21st to end	Night	16% 7% 2 6% 4 4 4 4 6% 7% 40%	2100
May	1st to 10th	Night	17% 8% 3 7% 4 5% 5% 4 6% 9% 32%	4267
	11th to 20th	Night	14% 8% 3 8% 5% 5% 4 4 5% 8% 35%	4086
	21st to end	Night	12% 6% 3 7% 5% 4 5% 4 6% 8% 40%	4127
June	1st to 10th	Night	9% 5% 2 6% 4 4 5% 4 6% 8% 47%	1600
	11th to 20th	Night	5% 3 2 5% 4 4 5% 4 8% 9% 53%	1600
	21st to end	Night	3 2 2 4 4 4 5% 5% 8% 13% 50%	1600
July	1st to 10th	Night	8% 5% 2 5% 4 5% 5% 5% 6% 7% 48%	3618
	11th to 20th	Night	5% 4 2 5% 4 5% 5% 5% 6% 12% 48%	3617
	21st to end	Night	5% 5% 2 6% 4 5% 5% 4 7% 14% 42%	4108
August	1st to 10th	Night	3 3 1 4 3 4 4 3 5% 8% 61%	3244
	11th to 20th	Night	5% 4 1 5% 4 4 4 4 6% 9% 53%	3200
	21st to end	Night	4 4 1 3 3 3 3 4 6% 8% 62%	3586
September	1st to 10th	Night	8% 5% 2 6% 3 3 3 3 4 6% 56%	2000
	11th to 20th	Night	8% 5% 2 5% 3 4 4 3 5% 7% 54%	2104
	21st to end	Night	12% 4 2 5% 3 4 3 3 5% 7% 54%	2200
October	1st to 10th	Night	7% 4 1 5% 4 3 3 2 4 6% 61%	2223
	11th to 20th	Night	13% 4 2 4 3 4 3 2 4 5% 56%	2400
	21st to end	Night	18% 7% 2 6% 3 3 3 3 4 5% 47%	2740
November	1st to 10th	Night	13% 5% 2 6% 2 3 3 2 4 6% 54%	2666
	11th to 20th	Night	13% 6% 2 4 4 3 3 3 4 6% 51%	2730
	21st to end	Night	17% 7% 3 5% 4 3 3 2 4 5% 48%	2730
December	1st to 10th	Night	17% 8% 2 7% 4 3 4 3 4 4 45%	4411
	11th to 20th	Night	18% 8% 2 5% 4 4 3 3 4 6% 44%	5339
	21st to end	Night	23% 11% 3 7% 4 4 4 3 4 5% 30%	7150

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	48% 4 13% 25% 8% 1	4692
	11th to 20th	Day	36% 4 6% 30% 22% 2	4922
	21st to end	Day	48% 4 9% 20% 13% 6%	5812
February	1st to 10th	Day	48% 4 11% 23% 12% 2	2082
	11th to 20th	Day	49% 3 10% 21% 13% 5%	2058
	21st to end	Day	49% 4 9% 19% 14% 5%	1730
March	1st to 10th	Day	49% 3 5% 20% 17% 6%	4580
	11th to 20th	Day	36% 4 8% 26% 22% 5%	4826
	21st to end	Day	40% 5% 10% 26% 17%	6100
April	1st to 10th	Day	38% 6% 11% 25% 18% 2	2520
	11th to 20th	Day	42% 6% 10% 22% 18% 4	2494
	21st to end	Day	43% 6% 11% 25% 14% 1	2520
May	1st to 10th	Day	51% 9% 12% 18% 10%	5884
	11th to 20th	Day	47% 9% 12% 21% 11% 1	5943
	21st to end	Day	42% 7% 10% 21% 17% 3	6737
June	1st to 10th	Day	33% 9% 14% 23% 20% 2	2800
	11th to 20th	Day	29% 8% 13% 27% 21% 3	2800
	21st to end	Day	31% 9% 16% 23% 16% 5%	2800
July	1st to 10th	Day	35% 7% 12% 28% 16% 2	6291
	11th to 20th	Day	31% 10% 17% 32% 9% 2	6285
	21st to end	Day	40% 9% 19% 24% 8% 1	6547
August	1st to 10th	Day	24% 7% 15% 31% 22% 1	3893
	11th to 20th	Day	34% 7% 13% 27% 18% 1	3885
	21st to end	Day	24% 5% 12% 35% 20% 3	4311
September	1st to 10th	Day	34% 7% 10% 25% 21% 4	2400
	11th to 20th	Day	34% 6% 9% 24% 25% 2	2275
	21st to end	Day	34% 5% 8% 23% 25% 5%	2200
October	1st to 10th	Day	18% 3 6% 19% 45% 10%	3537
	11th to 20th	Day	23% 3 6% 25% 30% 13%	3240
	21st to end	Day	31% 3 6% 27% 28% 5%	3362
November	1st to 10th	Day	34% 4 9% 25% 23% 5%	1852
	11th to 20th	Day	38% 4 7% 22% 23% 5%	1890
	21st to end	Day	45% 3 7% 25% 17% 3	1890
December	1st to 10th	Day	41% 4 8% 29% 17% 1	2974
	11th to 20th	Day	46% 5% 10% 24% 14% 3	3085
	21st to end	Day	58% 5% 12% 17% 8% 1	4070
January	1st to 10th	Night	48% 4 12% 26% 10% 1	8233
	11th to 20th	Night	40% 5% 6% 24% 23% 3	8063
	21st to end	Night	48% 4 9% 22% 14% 3	8402
February	1st to 10th	Night	52% 4 9% 20% 13% 1	2536
	11th to 20th	Night	48% 4 7% 22% 16% 3	2459
	21st to end	Night	47% 5% 8% 18% 18% 4	2076
March	1st to 10th	Night	50% 5% 5% 15% 19% 6%	5493
	11th to 20th	Night	36% 5% 9% 22% 17% 11%	5383
	21st to end	Night	43% 5% 9% 27% 14% 2	5072
April	1st to 10th	Night	35% 5% 12% 26% 18% 4	2100
	11th to 20th	Night	36% 5% 11% 22% 20% 6%	2075
	21st to end	Night	42% 6% 10% 22% 18% 2	2100
May	1st to 10th	Night	47% 8% 14% 21% 9% 1	4296
	11th to 20th	Night	47% 7% 13% 20% 12% 1	4087
	21st to end	Night	39% 9% 11% 24% 15% 2	4135
June	1st to 10th	Night	32% 8% 12% 22% 23% 3	1600
	11th to 20th	Night	25% 8% 15% 25% 22% 5%	1600
	21st to end	Night	22% 9% 17% 26% 18% 7%	1600
July	1st to 10th	Night	33% 7% 12% 25% 20% 3	3580
	11th to 20th	Night	27% 9% 20% 29% 13% 2	3572
	21st to end	Night	33% 8% 21% 29% 10%	3991
August	1st to 10th	Night	20% 7% 15% 36% 21% 1	3232
	11th to 20th	Night	27% 7% 17% 28% 18% 3	3230
	21st to end	Night	20% 5% 11% 36% 26% 3	3586
September	1st to 10th	Night	29% 6% 9% 28% 22% 6%	2000
	11th to 20th	Night	30% 6% 8% 27% 25% 4	2104
	21st to end	Night	31% 4 10% 24% 24% 7%	2200
October	1st to 10th	Night	18% 3 5% 15% 45% 15%	3639
	11th to 20th	Night	20% 3 5% 20% 40% 12%	3899
	21st to end	Night	30% 3 6% 23% 27% 10%	4413
November	1st to 10th	Night	32% 3 8% 26% 25% 6%	2666
	11th to 20th	Night	35% 3 7% 24% 23% 8%	2730
	21st to end	Night	40% 3 7% 25% 21% 3	2730
December	1st to 10th	Night	44% 4 8% 25% 18% 1	4411
	11th to 20th	Night	43% 4 10% 23% 19% 2	5341
	21st to end	Night	55% 6% 9% 20% 9% 2	7150

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% 15% 32% 20% 5% 1	330
	11th to 20th	Day	27% 20% 32% 18% 3 1	330
	21st to end	Day	21% 18% 41% 15% 4	363
February	1st to 10th	Day	26% 15% 35% 18% 5% 1	330
	11th to 20th	Day	28% 19% 35% 15% 2 1	330
	21st to end	Day	27% 16% 35% 16% 5%	273
March	1st to 10th	Day	24% 14% 39% 17% 5% 1	330
	11th to 20th	Day	25% 18% 35% 17% 4 1	330
	21st to end	Day	22% 17% 34% 19% 7% 1	593
April	1st to 10th	Day	19% 13% 33% 25% 9% 1	540
	11th to 20th	Day	19% 16% 28% 24% 11% 2	532
	21st to end	Day	18% 11% 33% 26% 9% 4	540
May	1st to 10th	Day	17% 14% 27% 26% 11% 3	543
	11th to 20th	Day	19% 7% 21% 26% 19% 8%	551
	21st to end	Day	13% 3 21% 29% 21% 12%	694
June	1st to 10th	Day	11% 5% 17% 26% 25% 16%	730
	11th to 20th	Day	7% 2 17% 32% 31% 12%	730
	21st to end	Day	7% 2 16% 35% 26% 15%	730
July	1st to 10th	Day	9% 3 10% 27% 27% 24%	721
	11th to 20th	Day	6% 3 10% 28% 36% 17%	718
	21st to end	Day	6% 3 11% 28% 33% 19%	784
August	1st to 10th	Day	10% 2 10% 27% 32% 19%	526
	11th to 20th	Day	11% 3 11% 25% 34% 16%	519
	21st to end	Day	9% 1 8% 25% 34% 23%	583
September	1st to 10th	Day	8% 4 11% 23% 34% 18%	530
	11th to 20th	Day	10% 2 8% 25% 34% 21%	530
	21st to end	Day	15% 5% 18% 25% 24% 12%	530
October	1st to 10th	Day	10% 3 15% 34% 29% 9%	503
	11th to 20th	Day	14% 8% 31% 28% 14% 5%	330
	21st to end	Day	26% 12% 27% 23% 10% 2	363
November	1st to 10th	Day	18% 10% 28% 27% 12% 5%	330
	11th to 20th	Day	13% 15% 32% 27% 12% 2	330
	21st to end	Day	25% 14% 25% 25% 10% 2	330
December	1st to 10th	Day	22% 15% 32% 18% 11% 2	330
	11th to 20th	Day	24% 16% 28% 22% 10%	330
	21st to end	Day	28% 15% 35% 19% 3 1	363
January	1st to 10th	Night	24% 11% 32% 29% 5%	1050
	11th to 20th	Night	24% 15% 35% 22% 5%	1050
	21st to end	Night	22% 9% 39% 29% 2	1155
February	1st to 10th	Night	24% 10% 36% 26% 3	856
	11th to 20th	Night	24% 12% 37% 25% 2	823
	21st to end	Night	23% 15% 35% 26% 2	692
March	1st to 10th	Night	22% 13% 30% 31% 5%	840
	11th to 20th	Night	22% 9% 36% 26% 7%	767
	21st to end	Night	21% 11% 29% 31% 7%	693
April	1st to 10th	Night	15% 10% 35% 31% 8%	630
	11th to 20th	Night	16% 10% 29% 31% 12% 1	623
	21st to end	Night	18% 6% 32% 32% 12% 1	630
May	1st to 10th	Night	17% 6% 28% 34% 14% 1	630
	11th to 20th	Night	15% 6% 17% 38% 22% 2	609
	21st to end	Night	8% 3 16% 40% 29% 4	650
June	1st to 10th	Night	11% 3 14% 38% 31% 3	600
	11th to 20th	Night	7% 1 10% 44% 37% 2	600
	21st to end	Night	4 2 12% 42% 35% 5%	600
July	1st to 10th	Night	8% 1 7% 29% 43% 11%	585
	11th to 20th	Night	6% 2 8% 30% 45% 9%	582
	21st to end	Night	6% 1 10% 31% 42% 10%	657
August	1st to 10th	Night	7% 2 7% 31% 46% 8%	597
	11th to 20th	Night	8% 2 10% 32% 42% 6%	594
	21st to end	Night	8% 1 5% 31% 46% 9%	660
September	1st to 10th	Night	10% 2 10% 34% 39% 6%	600
	11th to 20th	Night	9% 1 8% 32% 42% 7%	704
	21st to end	Night	13% 3 15% 35% 29% 6%	800
October	1st to 10th	Night	9% 4 17% 36% 30% 5%	800
	11th to 20th	Night	15% 5% 25% 34% 20% 2	800
	21st to end	Night	22% 8% 27% 31% 12% 1	880
November	1st to 10th	Night	15% 7% 27% 36% 15% 1	820
	11th to 20th	Night	15% 8% 33% 31% 12%	840
	21st to end	Night	21% 9% 28% 30% 11% 1	840
December	1st to 10th	Night	24% 10% 29% 30% 7% 1	858
	11th to 20th	Night	23% 7% 31% 32% 7%	1050
	21st to end	Night	28% 10% 30% 27% 4	1155

Page generated at 2026-05-14 00:58:59. Version ac07

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