Paxton
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Paxton clear sky chart from 2005-11-06 to 2024-12-06.

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% 9% 3 8% 5% 4 5% 4 6% 8% 37%	101486
	Night	14% 9% 4 7% 4 4 4 3 5% 6% 39%	98285
Transparency	Day	43% 6% 12% 22% 14% 2	105078
	Night	43% 5% 11% 22% 15% 2	102834
Seeing	Day	16% 10% 28% 25% 16% 6%	15806
	Night	17% 10% 30% 29% 13% 1	25660

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	13% 14% 7% 16% 6% 4 4 3 5% 5% 22%	2527
	11th to 20th	Day	13% 13% 5% 14% 8% 7% 4 6% 7% 5% 18%	2530
	21st to end	Day	20% 23% 7% 11% 4 4 3 2 4 5% 18%	2947
February	1st to 10th	Day	17% 12% 4 10% 6% 5% 5% 3 4 5% 29%	1794
	11th to 20th	Day	15% 11% 3 8% 6% 5% 4 3 5% 7% 32%	1848
	21st to end	Day	15% 15% 5% 10% 4 3 4 2 5% 6% 31%	1570
March	1st to 10th	Day	17% 19% 4 8% 4 3 4 2 3 4 31%	3120
	11th to 20th	Day	9% 9% 3 6% 5% 4 5% 4 6% 8% 41%	3269
	21st to end	Day	15% 12% 6% 10% 5% 5% 5% 4 5% 6% 27%	4165
April	1st to 10th	Day	15% 11% 4 7% 5% 4 4 4 6% 6% 34%	2280
	11th to 20th	Day	16% 9% 3 6% 5% 5% 4 4 5% 7% 37%	2254
	21st to end	Day	20% 8% 3 8% 5% 4 4 3 5% 6% 34%	2348
May	1st to 10th	Day	17% 7% 3 7% 5% 5% 6% 5% 6% 9% 30%	4082
	11th to 20th	Day	16% 8% 3 7% 4 4 5% 3 5% 7% 38%	4176
	21st to end	Day	8% 5% 2 6% 4 4 5% 4 6% 9% 45%	4824
June	1st to 10th	Day	9% 5% 2 6% 4 5% 5% 4 7% 8% 43%	2660
	11th to 20th	Day	8% 5% 1 7% 5% 4 5% 4 7% 8% 46%	2660
	21st to end	Day	9% 6% 2 7% 5% 5% 5% 5% 7% 9% 39%	2660
July	1st to 10th	Day	13% 5% 2 7% 5% 5% 6% 5% 7% 11% 35%	4440
	11th to 20th	Day	6% 5% 2 5% 5% 5% 5% 4 8% 11% 44%	4440
	21st to end	Day	9% 6% 2 6% 5% 6% 5% 4 7% 9% 39%	4813
August	1st to 10th	Day	6% 4 2 6% 4 4 5% 4 6% 9% 50%	4164
	11th to 20th	Day	8% 5% 2 7% 4 4 5% 4 8% 11% 42%	3729
	21st to end	Day	5% 5% 2 5% 4 4 5% 3 7% 11% 49%	4180
September	1st to 10th	Day	11% 5% 2 6% 5% 4 4 4 6% 7% 46%	2280
	11th to 20th	Day	10% 5% 2 5% 3 3 4 4 5% 8% 50%	2152
	21st to end	Day	11% 5% 2 5% 4 5% 5% 4 6% 7% 46%	2090
October	1st to 10th	Day	11% 6% 2 6% 4 5% 5% 3 5% 6% 47%	2058
	11th to 20th	Day	17% 7% 2 6% 4 3 4 4 6% 7% 42%	1900
	21st to end	Day	18% 9% 3 7% 5% 4 4 4 6% 6% 35%	1893
November	1st to 10th	Day	12% 7% 2 5% 4 3 3 4 5% 6% 49%	1762
	11th to 20th	Day	16% 12% 3 6% 4 5% 3 3 4 5% 39%	1800
	21st to end	Day	17% 10% 4 10% 5% 4 3 2 5% 5% 36%	1800
December	1st to 10th	Day	15% 14% 6% 10% 6% 4 4 3 5% 6% 28%	1570
	11th to 20th	Day	14% 13% 4 12% 6% 4 5% 3 5% 6% 28%	1918
	21st to end	Day	20% 20% 7% 13% 5% 5% 4 3 3 4 14%	2783
January	1st to 10th	Night	15% 16% 6% 10% 4 4 4 3 4 4 28%	4428
	11th to 20th	Night	14% 18% 7% 12% 6% 5% 5% 3 5% 4 20%	4440
	21st to end	Night	23% 16% 7% 10% 4 4 3 2 4 4 23%	4718
February	1st to 10th	Night	17% 13% 4 8% 6% 5% 4 3 4 5% 30%	2384
	11th to 20th	Night	13% 12% 3 8% 5% 4 5% 3 5% 6% 35%	2218
	21st to end	Night	18% 12% 3 9% 5% 3 4 3 5% 6% 33%	1884
March	1st to 10th	Night	17% 14% 3 6% 4 3 3 3 4 6% 36%	3733
	11th to 20th	Night	11% 7% 3 6% 5% 4 3 3 5% 7% 45%	3717
	21st to end	Night	18% 9% 4 10% 5% 5% 4 4 6% 6% 29%	3466
April	1st to 10th	Night	12% 9% 3 7% 4 5% 4 3 5% 7% 40%	1900
	11th to 20th	Night	17% 8% 3 5% 5% 4 4 3 4 6% 41%	1875
	21st to end	Night	19% 8% 3 5% 5% 4 5% 3 4 6% 37%	1830
May	1st to 10th	Night	16% 10% 3 7% 4 4 5% 3 6% 8% 34%	2813
	11th to 20th	Night	16% 7% 2 6% 5% 3 4 3 6% 9% 38%	2705
	21st to end	Night	10% 6% 2 6% 4 5% 4 3 6% 8% 45%	2743
June	1st to 10th	Night	9% 5% 2 6% 4 3 4 4 5% 7% 50%	1520
	11th to 20th	Night	8% 5% 2 5% 4 4 4 4 6% 8% 49%	1520
	21st to end	Night	7% 5% 2 8% 5% 5% 5% 4 7% 11% 42%	1520
July	1st to 10th	Night	11% 4 2 5% 4 4 5% 4 7% 10% 44%	2530
	11th to 20th	Night	4 3 2 4 4 4 4 3 7% 9% 56%	2530
	21st to end	Night	6% 6% 2 7% 5% 5% 5% 4 6% 9% 45%	2750
August	1st to 10th	Night	6% 4 2 5% 3 4 4 4 6% 9% 52%	2765
	11th to 20th	Night	6% 5% 2 6% 4 5% 5% 3 7% 8% 50%	3100
	21st to end	Night	6% 4 2 6% 3 4 4 3 5% 8% 54%	3476
September	1st to 10th	Night	12% 4 2 5% 4 3 3 3 5% 7% 54%	1900
	11th to 20th	Night	8% 4 1 4 4 3 4 3 5% 6% 56%	2008
	21st to end	Night	10% 6% 2 6% 4 4 5% 4 6% 6% 47%	2090
October	1st to 10th	Night	11% 5% 2 5% 4 4 3 3 4 5% 55%	2118
	11th to 20th	Night	14% 7% 2 5% 3 3 3 2 5% 6% 50%	2280
	21st to end	Night	18% 8% 3 6% 5% 3 4 3 4 6% 40%	2703
November	1st to 10th	Night	11% 6% 3 7% 3 3 4 3 5% 6% 49%	2536
	11th to 20th	Night	12% 9% 3 8% 5% 4 4 3 5% 6% 41%	2600
	21st to end	Night	17% 12% 4 9% 4 3 3 3 4 5% 36%	2600
December	1st to 10th	Night	16% 11% 4 9% 5% 4 4 4 5% 6% 33%	2722
	11th to 20th	Night	16% 12% 5% 9% 5% 4 3 3 4 5% 34%	3279
	21st to end	Night	24% 18% 8% 12% 5% 4 4 3 3 4 16%	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	62% 5% 11% 15% 6%	2528
	11th to 20th	Day	65% 5% 11% 10% 8% 1	2530
	21st to end	Day	69% 4 9% 13% 4	2947
February	1st to 10th	Day	57% 4 11% 17% 9% 2	1794
	11th to 20th	Day	52% 5% 11% 22% 10% 1	1858
	21st to end	Day	54% 5% 10% 20% 8% 2	1570
March	1st to 10th	Day	58% 4 9% 16% 12% 2	3120
	11th to 20th	Day	38% 7% 13% 28% 14% 1	3269
	21st to end	Day	54% 8% 15% 18% 4 1	4165
April	1st to 10th	Day	48% 6% 13% 20% 13%	2280
	11th to 20th	Day	45% 6% 12% 22% 12% 4	2254
	21st to end	Day	51% 5% 12% 18% 12% 2	2348
May	1st to 10th	Day	46% 10% 13% 23% 8%	4120
	11th to 20th	Day	44% 7% 12% 27% 9% 1	4180
	21st to end	Day	32% 8% 13% 21% 23% 4	4837
June	1st to 10th	Day	35% 9% 14% 23% 16% 3	2660
	11th to 20th	Day	33% 7% 11% 24% 21% 4	2660
	21st to end	Day	39% 8% 14% 21% 15% 3	2660
July	1st to 10th	Day	42% 7% 13% 26% 11% 2	4371
	11th to 20th	Day	32% 7% 15% 29% 16% 1	4365
	21st to end	Day	39% 8% 15% 19% 17% 2	4662
August	1st to 10th	Day	30% 7% 17% 30% 15% 1	4149
	11th to 20th	Day	33% 7% 15% 27% 16% 1	3765
	21st to end	Day	28% 7% 15% 31% 15% 4	4179
September	1st to 10th	Day	36% 6% 12% 24% 18% 5%	2280
	11th to 20th	Day	31% 5% 11% 25% 23% 5%	2152
	21st to end	Day	36% 5% 10% 25% 22% 2	2090
October	1st to 10th	Day	27% 3 7% 25% 35% 3	3422
	11th to 20th	Day	30% 4 10% 24% 31% 2	3140
	21st to end	Day	42% 4 9% 23% 21% 2	3093
November	1st to 10th	Day	35% 5% 14% 25% 17% 4	1762
	11th to 20th	Day	48% 4 10% 22% 13% 3	1800
	21st to end	Day	52% 4 11% 19% 12% 1	1800
December	1st to 10th	Day	57% 5% 11% 19% 7% 1	1570
	11th to 20th	Day	56% 5% 9% 23% 6% 1	1915
	21st to end	Day	73% 6% 9% 9% 4	2783
January	1st to 10th	Night	57% 6% 11% 17% 8%	4428
	11th to 20th	Night	67% 3 9% 14% 7%	4440
	21st to end	Night	66% 4 9% 14% 7% 1	4718
February	1st to 10th	Night	56% 5% 11% 17% 10% 2	2384
	11th to 20th	Night	49% 5% 11% 22% 12% 2	2219
	21st to end	Night	52% 5% 11% 20% 10% 3	1884
March	1st to 10th	Night	49% 6% 11% 22% 10% 2	3733
	11th to 20th	Night	36% 7% 11% 25% 19% 2	3717
	21st to end	Night	52% 9% 12% 20% 6% 1	3466
April	1st to 10th	Night	43% 7% 12% 22% 14% 2	1900
	11th to 20th	Night	44% 5% 9% 22% 17% 4	1875
	21st to end	Night	49% 5% 11% 20% 12% 4	1830
May	1st to 10th	Night	47% 7% 13% 23% 11%	2840
	11th to 20th	Night	41% 8% 15% 25% 11% 1	2706
	21st to end	Night	35% 8% 12% 20% 20% 5%	2751
June	1st to 10th	Night	32% 6% 12% 28% 18% 4	1520
	11th to 20th	Night	30% 6% 12% 26% 21% 4	1520
	21st to end	Night	35% 6% 17% 22% 17% 4	1520
July	1st to 10th	Night	36% 5% 15% 28% 11% 5%	2490
	11th to 20th	Night	23% 6% 15% 31% 24% 2	2482
	21st to end	Night	34% 6% 17% 20% 18% 4	2662
August	1st to 10th	Night	27% 7% 18% 30% 17% 2	2756
	11th to 20th	Night	30% 7% 15% 28% 19% 1	3130
	21st to end	Night	28% 5% 12% 33% 18% 4	3476
September	1st to 10th	Night	30% 6% 10% 26% 22% 7%	1900
	11th to 20th	Night	27% 5% 9% 26% 28% 5%	2008
	21st to end	Night	35% 6% 8% 25% 23% 3	2090
October	1st to 10th	Night	20% 3 7% 31% 36% 3	3534
	11th to 20th	Night	26% 3 8% 26% 33% 3	3779
	21st to end	Night	37% 3 9% 23% 23% 5%	4453
November	1st to 10th	Night	35% 5% 11% 27% 18% 4	2536
	11th to 20th	Night	44% 4 11% 23% 16% 3	2600
	21st to end	Night	51% 4 9% 23% 13% 1	2600
December	1st to 10th	Night	52% 4 12% 21% 10% 1	2722
	11th to 20th	Night	53% 4 11% 19% 12% 1	3281
	21st to end	Night	72% 5% 7% 10% 5%	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	22% 16% 33% 19% 9%	270
	11th to 20th	Day	24% 19% 39% 13% 5%	270
	21st to end	Day	24% 18% 32% 20% 5%	297
February	1st to 10th	Day	24% 15% 36% 20% 5%	270
	11th to 20th	Day	24% 13% 40% 17% 5%	270
	21st to end	Day	25% 17% 41% 14% 2	225
March	1st to 10th	Day	20% 23% 38% 17% 2	270
	11th to 20th	Day	25% 18% 36% 16% 4	294
	21st to end	Day	29% 15% 30% 17% 7% 1	506
April	1st to 10th	Day	22% 13% 35% 22% 7% 1	460
	11th to 20th	Day	20% 18% 31% 17% 12% 2	452
	21st to end	Day	23% 15% 33% 21% 6% 2	460
May	1st to 10th	Day	20% 10% 34% 25% 8% 2	463
	11th to 20th	Day	21% 10% 25% 26% 14% 5%	543
	21st to end	Day	11% 7% 32% 25% 15% 9%	734
June	1st to 10th	Day	10% 8% 26% 32% 20% 6%	680
	11th to 20th	Day	10% 5% 28% 31% 21% 6%	680
	21st to end	Day	11% 8% 31% 28% 17% 5%	680
July	1st to 10th	Day	11% 3 17% 30% 22% 17%	671
	11th to 20th	Day	6% 3 21% 33% 25% 12%	668
	21st to end	Day	9% 3 18% 33% 27% 9%	739
August	1st to 10th	Day	6% 2 15% 33% 29% 16%	576
	11th to 20th	Day	9% 3 19% 29% 29% 12%	479
	21st to end	Day	6% 2 14% 31% 34% 14%	539
September	1st to 10th	Day	11% 6% 17% 29% 29% 9%	490
	11th to 20th	Day	9% 4 13% 28% 30% 16%	490
	21st to end	Day	14% 8% 26% 22% 20% 11%	490
October	1st to 10th	Day	13% 6% 27% 30% 18% 7%	458
	11th to 20th	Day	14% 21% 30% 25% 8% 2	300
	21st to end	Day	31% 15% 32% 17% 5% 1	330
November	1st to 10th	Day	14% 13% 35% 24% 10% 5%	300
	11th to 20th	Day	23% 17% 33% 18% 8% 1	300
	21st to end	Day	23% 13% 36% 25% 3	300
December	1st to 10th	Day	16% 18% 42% 16% 7% 1	285
	11th to 20th	Day	17% 15% 41% 21% 5% 1	270
	21st to end	Day	26% 19% 36% 16% 4	297
January	1st to 10th	Night	22% 13% 39% 22% 3	950
	11th to 20th	Night	22% 16% 37% 20% 4	950
	21st to end	Night	21% 14% 37% 25% 4	1045
February	1st to 10th	Night	26% 12% 36% 23% 3	864
	11th to 20th	Night	19% 16% 36% 26% 3	743
	21st to end	Night	25% 14% 38% 20% 3	628
March	1st to 10th	Night	21% 15% 36% 24% 5%	760
	11th to 20th	Night	18% 14% 38% 24% 6% 1	741
	21st to end	Night	23% 10% 37% 25% 4	627
April	1st to 10th	Night	17% 13% 38% 26% 6%	570
	11th to 20th	Night	19% 13% 35% 25% 9%	563
	21st to end	Night	23% 10% 34% 25% 7% 1	570
May	1st to 10th	Night	18% 8% 37% 29% 8%	570
	11th to 20th	Night	18% 5% 28% 34% 13% 2	561
	21st to end	Night	11% 5% 28% 35% 19% 2	617
June	1st to 10th	Night	12% 4 25% 44% 16%	570
	11th to 20th	Night	11% 3 26% 42% 17% 1	570
	21st to end	Night	8% 4 26% 41% 20% 1	570
July	1st to 10th	Night	11% 2 16% 35% 33% 4	555
	11th to 20th	Night	5% 3 19% 41% 28% 4	552
	21st to end	Night	6% 2 14% 45% 31% 2	624
August	1st to 10th	Night	7% 2 12% 43% 31% 4	567
	11th to 20th	Night	7% 1 12% 45% 31% 4	564
	21st to end	Night	7% 2 15% 35% 38% 4	627
September	1st to 10th	Night	13% 4 14% 39% 27% 4	570
	11th to 20th	Night	9% 4 14% 39% 31% 3	678
	21st to end	Night	13% 7% 21% 31% 26% 3	760
October	1st to 10th	Night	14% 5% 22% 36% 20% 3	760
	11th to 20th	Night	18% 12% 30% 28% 12%	760
	21st to end	Night	22% 13% 35% 24% 6%	836
November	1st to 10th	Night	14% 9% 42% 25% 9% 1	780
	11th to 20th	Night	17% 16% 35% 26% 6% 1	800
	21st to end	Night	22% 16% 32% 24% 6%	800
December	1st to 10th	Night	21% 13% 38% 24% 3 1	963
	11th to 20th	Night	23% 11% 32% 27% 6%	950
	21st to end	Night	29% 14% 33% 21% 2	1045

Page generated at 2024-12-03 05:45:15. Version ac07

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