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 2024-08-15.

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% 7% 2 6% 4 4 4 4 6% 7% 41%	95424
	Night	14% 7% 2 6% 4 4 4 3 5% 7% 44%	93314
Transparency	Day	40% 7% 11% 24% 16% 3	95181
	Night	39% 6% 10% 24% 17% 4	93165
Seeing	Day	15% 7% 21% 26% 21% 10%	15150
	Night	16% 6% 24% 32% 19% 3	24930

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	15% 10% 3 9% 5% 4 4 3 5% 5% 37%	2527
	11th to 20th	Day	18% 8% 3 5% 4 4 4 3 4 5% 41%	2630
	21st to end	Day	24% 11% 4 9% 4 4 4 3 4 5% 30%	3135
February	1st to 10th	Day	18% 11% 3 6% 5% 3 3 3 6% 6% 36%	1883
	11th to 20th	Day	18% 10% 4 7% 4 4 4 3 4 5% 39%	1848
	21st to end	Day	18% 9% 4 8% 5% 4 4 2 4 6% 35%	1570
March	1st to 10th	Day	19% 13% 3 7% 4 4 3 3 4 5% 34%	3120
	11th to 20th	Day	14% 7% 2 5% 3 3 3 2 4 6% 50%	3306
	21st to end	Day	12% 8% 3 7% 5% 4 5% 3 6% 6% 42%	4164
April	1st to 10th	Day	13% 6% 2 6% 3 4 4 4 5% 8% 45%	2280
	11th to 20th	Day	13% 9% 2 8% 5% 4 4 4 5% 6% 41%	2254
	21st to end	Day	17% 7% 3 6% 4 4 4 4 5% 7% 40%	2280
May	1st to 10th	Day	15% 8% 2 7% 4 5% 5% 5% 7% 10% 32%	3983
	11th to 20th	Day	17% 7% 2 7% 4 4 5% 4 5% 8% 37%	4081
	21st to end	Day	11% 6% 2 7% 5% 5% 5% 4 7% 8% 40%	4682
June	1st to 10th	Day	9% 5% 1 5% 4 5% 6% 4 8% 9% 44%	2660
	11th to 20th	Day	5% 3 2 5% 5% 4 5% 5% 6% 10% 49%	2660
	21st to end	Day	5% 5% 2 5% 5% 5% 6% 5% 8% 10% 45%	2660
July	1st to 10th	Day	9% 5% 2 6% 5% 5% 6% 5% 7% 10% 40%	4440
	11th to 20th	Day	6% 3 1 5% 4 4 5% 4 7% 10% 49%	4440
	21st to end	Day	9% 9% 4 9% 7% 6% 6% 5% 7% 9% 31%	4685
August	1st to 10th	Day	8% 5% 2 5% 4 5% 5% 4 6% 10% 46%	2268
	11th to 20th	Day	9% 5% 2 6% 5% 5% 6% 4 7% 10% 42%	2174
	21st to end	Day	7% 4 2 6% 4 5% 5% 4 8% 10% 45%	2376
September	1st to 10th	Day	10% 6% 2 5% 4 4 4 4 6% 8% 46%	2160
	11th to 20th	Day	10% 5% 2 5% 4 5% 4 4 5% 7% 49%	2048
	21st to end	Day	11% 5% 2 4 4 3 5% 3 4 7% 53%	1980
October	1st to 10th	Day	10% 4 2 5% 3 3 4 3 4 6% 57%	1957
	11th to 20th	Day	14% 5% 2 5% 4 3 3 2 4 6% 51%	1800
	21st to end	Day	20% 6% 2 4 3 3 3 3 4 5% 46%	1889
November	1st to 10th	Day	10% 5% 2 5% 3 4 3 3 5% 6% 53%	1672
	11th to 20th	Day	15% 8% 2 5% 4 3 3 3 5% 5% 48%	1710
	21st to end	Day	18% 9% 2 5% 3 3 3 3 5% 5% 42%	1710
December	1st to 10th	Day	18% 9% 2 6% 4 3 4 4 5% 6% 39%	1691
	11th to 20th	Day	16% 9% 3 8% 5% 5% 5% 4 6% 5% 36%	1918
	21st to end	Day	20% 13% 4 8% 5% 4 4 3 4 5% 31%	2783
January	1st to 10th	Night	19% 8% 3 5% 3 4 4 4 5% 7% 39%	4428
	11th to 20th	Night	15% 10% 4 7% 5% 4 4 4 5% 6% 36%	4335
	21st to end	Night	25% 10% 4 5% 4 3 3 3 5% 6% 32%	4532
February	1st to 10th	Night	20% 11% 3 8% 4 3 3 3 4 4 35%	2295
	11th to 20th	Night	17% 8% 3 8% 4 4 3 3 4 6% 41%	2218
	21st to end	Night	18% 9% 3 7% 5% 4 4 4 4 5% 38%	1884
March	1st to 10th	Night	24% 10% 3 6% 4 3 3 3 4 5% 36%	3733
	11th to 20th	Night	13% 7% 2 5% 4 4 3 4 4 6% 48%	3682
	21st to end	Night	14% 8% 3 7% 5% 4 4 4 5% 7% 41%	3466
April	1st to 10th	Night	13% 5% 2 5% 3 3 4 3 6% 8% 48%	1900
	11th to 20th	Night	15% 6% 2 5% 4 3 3 3 5% 7% 46%	1875
	21st to end	Night	16% 7% 2 6% 4 4 4 4 6% 7% 41%	1900
May	1st to 10th	Night	18% 7% 2 5% 3 4 4 4 6% 10% 38%	2912
	11th to 20th	Night	13% 6% 2 7% 5% 4 3 3 5% 7% 44%	2812
	21st to end	Night	8% 5% 3 7% 4 4 5% 4 7% 10% 43%	2876
June	1st to 10th	Night	9% 5% 2 6% 4 4 5% 4 6% 8% 47%	1520
	11th to 20th	Night	4 3 1 5% 3 4 5% 4 8% 9% 54%	1520
	21st to end	Night	3 2 1 4 4 4 5% 5% 8% 13% 50%	1520
July	1st to 10th	Night	9% 5% 2 5% 4 5% 5% 5% 6% 8% 47%	2530
	11th to 20th	Night	5% 4 2 5% 3 4 3 3 5% 10% 56%	2530
	21st to end	Night	7% 7% 3 9% 6% 6% 5% 5% 7% 9% 37%	2856
August	1st to 10th	Night	5% 4 2 5% 4 4 5% 4 6% 10% 51%	1890
	11th to 20th	Night	7% 5% 1 4 4 4 4 4 7% 9% 52%	1826
	21st to end	Night	7% 5% 2 4 4 4 4 5% 7% 9% 51%	1980
September	1st to 10th	Night	9% 5% 2 6% 3 3 3 4 4 6% 55%	1800
	11th to 20th	Night	8% 5% 2 5% 3 3 4 3 4 7% 54%	1893
	21st to end	Night	10% 4 1 4 3 4 3 3 5% 7% 56%	1980
October	1st to 10th	Night	7% 4 2 5% 4 3 3 2 5% 6% 59%	2000
	11th to 20th	Night	14% 5% 2 5% 3 4 3 2 4 5% 53%	2160
	21st to end	Night	19% 6% 2 6% 3 4 4 3 4 5% 46%	2466
November	1st to 10th	Night	12% 5% 2 5% 2 2 2 2 4 7% 56%	2406
	11th to 20th	Night	14% 6% 2 4 3 3 3 3 4 6% 51%	2470
	21st to end	Night	17% 7% 2 5% 4 3 3 2 4 5% 49%	2470
December	1st to 10th	Night	19% 9% 2 6% 4 3 4 3 5% 5% 39%	2486
	11th to 20th	Night	17% 9% 2 5% 4 4 3 3 4 5% 43%	3279
	21st to end	Night	18% 12% 4 8% 5% 5% 5% 3 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	47% 5% 8% 27% 11% 2	2528
	11th to 20th	Day	46% 5% 9% 24% 15% 2	2630
	21st to end	Day	56% 4 9% 19% 10% 2	3135
February	1st to 10th	Day	48% 4 9% 24% 13% 2	1883
	11th to 20th	Day	48% 4 10% 21% 13% 5%	1858
	21st to end	Day	50% 4 9% 18% 13% 6%	1570
March	1st to 10th	Day	53% 4 6% 18% 12% 7%	3120
	11th to 20th	Day	37% 4 9% 27% 17% 5%	3306
	21st to end	Day	40% 7% 12% 22% 18% 1	4164
April	1st to 10th	Day	37% 6% 11% 26% 18% 2	2280
	11th to 20th	Day	42% 5% 9% 22% 18% 4	2254
	21st to end	Day	44% 6% 10% 25% 14% 2	2280
May	1st to 10th	Day	43% 11% 14% 20% 12% 1	4019
	11th to 20th	Day	43% 10% 10% 24% 12% 1	4085
	21st to end	Day	38% 9% 12% 19% 21% 1	4695
June	1st to 10th	Day	32% 9% 14% 22% 21% 2	2660
	11th to 20th	Day	27% 8% 14% 27% 22% 3	2660
	21st to end	Day	31% 9% 16% 23% 16% 5%	2660
July	1st to 10th	Day	36% 7% 15% 27% 12% 3	4371
	11th to 20th	Day	28% 8% 13% 37% 13% 2	4365
	21st to end	Day	48% 8% 13% 21% 9% 1	4537
August	1st to 10th	Day	32% 8% 17% 27% 15% 1	2256
	11th to 20th	Day	35% 9% 14% 25% 15% 1	2174
	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	44% 5% 9% 29% 12% 1	4428
	11th to 20th	Night	46% 6% 9% 23% 13% 2	4335
	21st to end	Night	51% 5% 9% 22% 11% 1	4532
February	1st to 10th	Night	53% 4 8% 20% 14% 1	2295
	11th to 20th	Night	46% 4 7% 22% 17% 3	2219
	21st to end	Night	49% 5% 9% 16% 17% 4	1884
March	1st to 10th	Night	51% 5% 7% 13% 18% 6%	3733
	11th to 20th	Night	37% 6% 11% 22% 16% 8%	3682
	21st to end	Night	42% 6% 9% 27% 15% 1	3466
April	1st to 10th	Night	34% 5% 11% 26% 20% 4	1900
	11th to 20th	Night	37% 5% 10% 22% 21% 7%	1875
	21st to end	Night	41% 6% 10% 23% 18% 2	1900
May	1st to 10th	Night	41% 9% 15% 23% 11% 1	2941
	11th to 20th	Night	40% 8% 12% 24% 15% 1	2813
	21st to end	Night	32% 11% 13% 26% 16% 2	2884
June	1st to 10th	Night	32% 8% 12% 22% 22% 3	1520
	11th to 20th	Night	23% 8% 15% 26% 23% 6%	1520
	21st to end	Night	22% 9% 18% 26% 18% 7%	1520
July	1st to 10th	Night	33% 8% 14% 27% 16% 3	2490
	11th to 20th	Night	24% 6% 14% 35% 18% 4	2482
	21st to end	Night	42% 8% 14% 24% 11%	2766
August	1st to 10th	Night	26% 9% 17% 28% 19% 1	1878
	11th to 20th	Night	26% 8% 16% 27% 20% 3	1826
	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% 32% 20% 3 1	270
	21st to end	Day	21% 13% 43% 18% 5%	297
February	1st to 10th	Day	27% 12% 34% 20% 5% 1	270
	11th to 20th	Day	26% 18% 36% 17% 3 1	270
	21st to end	Day	28% 15% 34% 17% 5%	225
March	1st to 10th	Day	21% 11% 41% 20% 6% 1	270
	11th to 20th	Day	23% 15% 37% 19% 4 1	270
	21st to end	Day	23% 16% 31% 21% 8% 1	505
April	1st to 10th	Day	18% 13% 31% 27% 11% 1	460
	11th to 20th	Day	19% 13% 28% 26% 13% 2	452
	21st to end	Day	19% 9% 32% 27% 9% 4	460
May	1st to 10th	Day	16% 13% 26% 28% 13% 4	463
	11th to 20th	Day	19% 7% 18% 28% 20% 9%	487
	21st to end	Day	12% 2 21% 29% 23% 13%	644
June	1st to 10th	Day	11% 5% 15% 27% 26% 16%	680
	11th to 20th	Day	6% 1 16% 34% 31% 12%	680
	21st to end	Day	7% 2 16% 35% 25% 15%	680
July	1st to 10th	Day	9% 3 10% 27% 26% 25%	671
	11th to 20th	Day	6% 3 10% 26% 37% 18%	668
	21st to end	Day	6% 3 12% 28% 32% 19%	730
August	1st to 10th	Day	9% 2 10% 27% 32% 20%	486
	11th to 20th	Day	12% 2 10% 25% 36% 16%	456
	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	22% 8% 39% 30% 2	1045
February	1st to 10th	Night	25% 9% 34% 28% 3	775
	11th to 20th	Night	22% 11% 39% 25% 3	743
	21st to end	Night	23% 14% 36% 25% 2	628
March	1st to 10th	Night	22% 11% 30% 32% 5%	760
	11th to 20th	Night	21% 8% 35% 28% 7%	694
	21st to end	Night	21% 10% 28% 33% 8%	627
April	1st to 10th	Night	14% 9% 35% 33% 9% 1	570
	11th to 20th	Night	17% 9% 28% 32% 13% 1	563
	21st to end	Night	19% 5% 31% 33% 11% 1	570
May	1st to 10th	Night	17% 5% 27% 34% 15% 2	570
	11th to 20th	Night	15% 5% 17% 39% 23% 2	561
	21st to end	Night	7% 2 15% 41% 30% 4	617
June	1st to 10th	Night	11% 3 14% 38% 32% 4	570
	11th to 20th	Night	5% 1 10% 44% 38% 2	570
	21st to end	Night	4 2 12% 42% 35% 5%	570
July	1st to 10th	Night	8% 1 7% 29% 43% 11%	555
	11th to 20th	Night	7% 3 8% 29% 45% 9%	552
	21st to end	Night	7% 1 11% 32% 41% 9%	624
August	1st to 10th	Night	7% 2 7% 31% 46% 8%	567
	11th to 20th	Night	8% 2 8% 33% 43% 6%	549
	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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