Medicine Hat
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Medicine Hat clear sky chart from 2005-11-06 to 2024-11-03.

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	8% 8% 3 7% 5% 4 5% 4 6% 8% 43%	101865
	Night	8% 8% 3 8% 5% 5% 5% 4 6% 8% 41%	97288
Transparency	Day	38% 7% 15% 26% 12% 2	101585
	Night	40% 7% 16% 24% 11% 2	97158
Seeing	Day	12% 9% 27% 30% 18% 4	15554
	Night	12% 8% 31% 35% 13% 1	24743

By Month

Percentage Cloud Cover SW (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	4 13% 5% 11% 6% 5% 6% 3 6% 9% 31%	2219
	11th to 20th	Day	5% 8% 4 13% 6% 7% 9% 6% 6% 7% 30%	2220
	21st to end	Day	4 11% 3 8% 5% 5% 4 3 5% 6% 45%	2666
February	1st to 10th	Day	8% 14% 5% 11% 7% 7% 5% 3 5% 6% 28%	1695
	11th to 20th	Day	8% 13% 5% 11% 6% 6% 6% 6% 7% 8% 25%	1665
	21st to end	Day	4 13% 6% 10% 8% 6% 7% 4 6% 7% 31%	1413
March	1st to 10th	Day	4 11% 4 11% 7% 5% 6% 4 6% 7% 34%	3292
	11th to 20th	Day	8% 8% 3 6% 5% 4 4 4 5% 9% 44%	3490
	21st to end	Day	10% 17% 5% 11% 4 4 5% 3 6% 8% 26%	3825
April	1st to 10th	Day	8% 10% 3 7% 7% 5% 5% 5% 8% 8% 35%	2301
	11th to 20th	Day	10% 12% 4 9% 5% 5% 5% 4 5% 7% 33%	2437
	21st to end	Day	11% 9% 4 9% 7% 4 4 4 5% 7% 36%	2470
May	1st to 10th	Day	18% 13% 3 8% 4 5% 4 3 5% 6% 31%	4366
	11th to 20th	Day	10% 5% 2 7% 5% 5% 6% 5% 8% 9% 37%	4496
	21st to end	Day	14% 7% 2 8% 5% 5% 6% 4 7% 8% 32%	5161
June	1st to 10th	Day	12% 6% 2 7% 4 5% 5% 5% 6% 9% 39%	2850
	11th to 20th	Day	16% 6% 3 6% 5% 4 6% 5% 7% 8% 33%	2850
	21st to end	Day	8% 3 2 5% 4 4 5% 5% 7% 8% 50%	2850
July	1st to 10th	Day	7% 3 2 6% 4 4 4 4 6% 8% 52%	4740
	11th to 20th	Day	5% 3 2 4 3 3 3 3 5% 7% 61%	4740
	21st to end	Day	3 2 1 3 2 2 3 3 4 6% 72%	5138
August	1st to 10th	Day	6% 4 2 5% 3 4 4 4 6% 8% 56%	4250
	11th to 20th	Day	5% 3 1 4 4 4 5% 4 6% 10% 55%	4028
	21st to end	Day	6% 2 1 3 3 3 3 3 5% 8% 63%	4521
September	1st to 10th	Day	10% 5% 2 5% 3 3 3 2 4 6% 56%	2331
	11th to 20th	Day	14% 5% 2 4 3 3 4 3 5% 8% 48%	2143
	21st to end	Day	8% 6% 2 5% 4 3 4 3 5% 7% 52%	2090
October	1st to 10th	Day	11% 7% 3 6% 4 4 5% 4 6% 7% 43%	1901
	11th to 20th	Day	7% 7% 2 7% 5% 6% 5% 4 7% 7% 43%	1900
	21st to end	Day	10% 10% 3 7% 4 4 5% 4 4 6% 42%	1867
November	1st to 10th	Day	13% 13% 4 9% 6% 5% 5% 4 5% 6% 31%	1504
	11th to 20th	Day	6% 10% 4 9% 6% 5% 5% 4 5% 8% 38%	1520
	21st to end	Day	6% 13% 3 10% 5% 5% 4 4 6% 9% 35%	1469
December	1st to 10th	Day	7% 15% 5% 9% 6% 6% 5% 4 6% 6% 31%	1330
	11th to 20th	Day	5% 12% 3 12% 6% 5% 6% 5% 5% 6% 34%	1685
	21st to end	Day	3 10% 3 8% 5% 3 4 3 5% 7% 48%	2442
January	1st to 10th	Night	4 10% 4 10% 6% 5% 5% 5% 6% 10% 34%	4726
	11th to 20th	Night	5% 9% 5% 11% 7% 6% 7% 5% 8% 8% 31%	4740
	21st to end	Night	5% 9% 4 10% 5% 5% 5% 4 6% 8% 40%	5022
February	1st to 10th	Night	9% 12% 4 10% 7% 5% 5% 4 5% 7% 31%	2484
	11th to 20th	Night	7% 12% 5% 10% 6% 6% 6% 5% 7% 7% 29%	2402
	21st to end	Night	5% 11% 4 10% 7% 5% 6% 4 6% 8% 34%	2041
March	1st to 10th	Night	5% 9% 5% 13% 7% 7% 5% 4 6% 7% 33%	3577
	11th to 20th	Night	9% 8% 3 6% 4 4 5% 4 7% 9% 43%	3490
	21st to end	Night	9% 17% 6% 12% 5% 6% 5% 4 7% 7% 21%	3828
April	1st to 10th	Night	9% 13% 3 9% 6% 5% 5% 4 6% 8% 33%	1876
	11th to 20th	Night	12% 9% 3 8% 5% 4 5% 4 6% 9% 34%	1691
	21st to end	Night	11% 8% 3 10% 4 5% 5% 4 5% 9% 37%	1710
May	1st to 10th	Night	21% 11% 3 6% 5% 4 4 3 4 6% 35%	2604
	11th to 20th	Night	8% 6% 2 7% 4 5% 5% 5% 8% 10% 40%	2402
	21st to end	Night	13% 8% 3 9% 7% 6% 6% 4 6% 8% 31%	2414
June	1st to 10th	Night	15% 6% 2 7% 5% 5% 4 5% 5% 7% 40%	1330
	11th to 20th	Night	13% 5% 2 5% 5% 5% 6% 5% 7% 7% 39%	1330
	21st to end	Night	6% 4 1 5% 3 3 5% 5% 6% 9% 53%	1330
July	1st to 10th	Night	7% 2 1 5% 4 3 5% 4 5% 8% 57%	2220
	11th to 20th	Night	4 2 1 4 3 3 4 4 6% 11% 58%	2220
	21st to end	Night	2 1 1 2 2 3 2 4 5% 8% 70%	2413
August	1st to 10th	Night	8% 4 1 5% 3 3 4 4 6% 9% 51%	2684
	11th to 20th	Night	5% 3 1 5% 4 4 5% 4 7% 11% 51%	2811
	21st to end	Night	10% 3 1 3 3 2 3 3 5% 8% 59%	3146
September	1st to 10th	Night	9% 4 1 5% 4 4 4 3 6% 7% 54%	1848
	11th to 20th	Night	13% 5% 2 5% 3 3 4 4 5% 7% 49%	2033
	21st to end	Night	8% 4 1 5% 4 4 4 3 7% 8% 53%	2090
October	1st to 10th	Night	12% 6% 2 6% 4 4 4 4 6% 8% 45%	2278
	11th to 20th	Night	9% 8% 2 6% 4 4 4 3 7% 8% 45%	2280
	21st to end	Night	9% 9% 3 9% 5% 5% 5% 4 5% 7% 39%	2712
November	1st to 10th	Night	10% 13% 3 8% 6% 4 4 3 5% 7% 36%	2619
	11th to 20th	Night	6% 11% 3 8% 6% 6% 4 4 6% 7% 39%	2660
	21st to end	Night	5% 13% 4 8% 5% 5% 4 4 5% 8% 39%	2707
December	1st to 10th	Night	7% 13% 4 10% 6% 5% 6% 4 6% 6% 33%	2850
	11th to 20th	Night	5% 9% 4 10% 6% 5% 5% 5% 7% 9% 36%	3506
	21st to end	Night	5% 8% 3 6% 4 4 5% 4 7% 6% 48%	5214

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% 8% 19% 20% 5%	2219
	11th to 20th	Day	52% 6% 13% 16% 12% 1	2220
	21st to end	Day	39% 8% 26% 24% 4	2666
February	1st to 10th	Day	56% 7% 14% 17% 7%	1695
	11th to 20th	Day	53% 8% 14% 18% 7%	1674
	21st to end	Day	52% 6% 13% 19% 9% 1	1413
March	1st to 10th	Day	44% 9% 16% 24% 7%	3292
	11th to 20th	Day	36% 7% 23% 24% 9%	3490
	21st to end	Day	53% 9% 18% 16% 5%	3825
April	1st to 10th	Day	45% 7% 15% 24% 9%	2301
	11th to 20th	Day	50% 6% 11% 24% 8% 1	2440
	21st to end	Day	47% 5% 13% 25% 8% 1	2470
May	1st to 10th	Day	53% 6% 12% 23% 6%	4366
	11th to 20th	Day	37% 9% 15% 28% 10% 1	4500
	21st to end	Day	45% 9% 15% 23% 8% 1	5162
June	1st to 10th	Day	40% 7% 17% 23% 11% 2	2850
	11th to 20th	Day	45% 7% 14% 21% 11% 1	2850
	21st to end	Day	30% 6% 18% 31% 13% 3	2850
July	1st to 10th	Day	28% 7% 16% 26% 19% 4	4666
	11th to 20th	Day	23% 5% 15% 33% 20% 4	4659
	21st to end	Day	14% 4 9% 30% 28% 15%	4976
August	1st to 10th	Day	26% 5% 11% 33% 21% 3	4233
	11th to 20th	Day	24% 6% 15% 40% 14% 2	4067
	21st to end	Day	21% 4 13% 39% 20% 2	4520
September	1st to 10th	Day	30% 4 13% 26% 19% 8%	2331
	11th to 20th	Day	35% 6% 14% 29% 14% 3	2143
	21st to end	Day	31% 6% 14% 31% 16% 3	2090
October	1st to 10th	Day	38% 7% 16% 27% 12% 1	1901
	11th to 20th	Day	39% 5% 17% 26% 12% 1	1900
	21st to end	Day	43% 6% 14% 26% 11%	1867
November	1st to 10th	Day	53% 7% 14% 17% 8% 1	1504
	11th to 20th	Day	44% 7% 19% 23% 7%	1520
	21st to end	Day	46% 6% 20% 21% 7% 1	1469
December	1st to 10th	Day	51% 8% 16% 17% 7% 1	1330
	11th to 20th	Day	47% 9% 19% 20% 4 1	1684
	21st to end	Day	35% 5% 15% 26% 16% 3	2442
January	1st to 10th	Night	43% 9% 22% 21% 4 1	4726
	11th to 20th	Night	49% 7% 15% 16% 12% 1	4740
	21st to end	Night	41% 7% 21% 25% 5% 1	5022
February	1st to 10th	Night	51% 7% 14% 18% 10% 1	2484
	11th to 20th	Night	50% 7% 16% 17% 9% 1	2403
	21st to end	Night	48% 5% 14% 23% 9% 1	2041
March	1st to 10th	Night	46% 10% 15% 21% 8%	3577
	11th to 20th	Night	36% 7% 22% 27% 8%	3490
	21st to end	Night	56% 10% 14% 15% 3 1	3828
April	1st to 10th	Night	49% 4 14% 23% 9%	1876
	11th to 20th	Night	47% 6% 11% 22% 13% 1	1691
	21st to end	Night	45% 5% 14% 25% 10% 2	1710
May	1st to 10th	Night	52% 5% 9% 23% 9% 1	2604
	11th to 20th	Night	34% 9% 16% 28% 13% 1	2403
	21st to end	Night	47% 9% 16% 22% 7% 1	2414
June	1st to 10th	Night	42% 7% 16% 24% 10% 2	1330
	11th to 20th	Night	39% 10% 11% 24% 14% 2	1330
	21st to end	Night	26% 6% 16% 33% 16% 3	1330
July	1st to 10th	Night	25% 6% 16% 28% 22% 3	2185
	11th to 20th	Night	20% 6% 12% 36% 20% 6%	2178
	21st to end	Night	14% 4 9% 31% 30% 14%	2337
August	1st to 10th	Night	28% 6% 13% 29% 21% 3	2677
	11th to 20th	Night	26% 6% 15% 34% 15% 3	2838
	21st to end	Night	25% 4 13% 35% 21% 3	3146
September	1st to 10th	Night	28% 7% 11% 25% 20% 9%	1848
	11th to 20th	Night	34% 6% 13% 27% 15% 5%	2033
	21st to end	Night	29% 5% 14% 31% 18% 3	2090
October	1st to 10th	Night	37% 6% 15% 26% 15% 2	2278
	11th to 20th	Night	36% 6% 15% 29% 13% 1	2280
	21st to end	Night	43% 6% 15% 26% 9% 1	2712
November	1st to 10th	Night	48% 7% 15% 21% 8% 1	2619
	11th to 20th	Night	43% 6% 20% 20% 10%	2660
	21st to end	Night	43% 6% 24% 18% 8% 1	2707
December	1st to 10th	Night	50% 8% 17% 17% 7% 1	2850
	11th to 20th	Night	43% 8% 25% 19% 4 1	3507
	21st to end	Night	34% 5% 15% 25% 15% 5%	5214

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	9% 6% 32% 31% 17% 6%	180
	11th to 20th	Day	11% 5% 37% 31% 16% 2	180
	21st to end	Day	12% 10% 32% 33% 12% 2	198
February	1st to 10th	Day	18% 12% 35% 25% 7% 2	263
	11th to 20th	Day	13% 6% 31% 31% 15% 3	270
	21st to end	Day	6% 8% 32% 36% 15% 3	225
March	1st to 10th	Day	11% 14% 32% 27% 13% 3	446
	11th to 20th	Day	9% 10% 33% 28% 14% 5%	460
	21st to end	Day	13% 11% 29% 28% 16% 3	506
April	1st to 10th	Day	12% 16% 32% 31% 8% 2	460
	11th to 20th	Day	12% 15% 31% 28% 13% 1	452
	21st to end	Day	17% 9% 26% 31% 14% 3	460
May	1st to 10th	Day	16% 7% 24% 27% 20% 6%	615
	11th to 20th	Day	13% 7% 24% 31% 20% 5%	675
	21st to end	Day	18% 7% 19% 26% 22% 8%	734
June	1st to 10th	Day	15% 12% 23% 30% 17% 4	680
	11th to 20th	Day	17% 12% 29% 27% 14% 2	680
	21st to end	Day	10% 7% 25% 32% 19% 7%	680
July	1st to 10th	Day	6% 4 21% 37% 26% 6%	671
	11th to 20th	Day	8% 4 23% 38% 22% 4	668
	21st to end	Day	5% 6% 21% 33% 28% 7%	739
August	1st to 10th	Day	6% 4 20% 41% 22% 8%	545
	11th to 20th	Day	7% 3 19% 35% 28% 8%	477
	21st to end	Day	7% 8% 23% 29% 26% 7%	539
September	1st to 10th	Day	11% 8% 26% 28% 24% 4	490
	11th to 20th	Day	14% 6% 24% 31% 21% 3	490
	21st to end	Day	13% 10% 29% 32% 11% 5%	490
October	1st to 10th	Day	16% 6% 27% 28% 18% 5%	301
	11th to 20th	Day	10% 11% 30% 31% 15% 4	300
	21st to end	Day	17% 11% 33% 24% 13% 2	330
November	1st to 10th	Day	27% 8% 29% 24% 12%	276
	11th to 20th	Day	12% 13% 37% 30% 6% 1	270
	21st to end	Day	10% 10% 39% 25% 10% 6%	246
December	1st to 10th	Day	9% 11% 41% 27% 11% 1	180
	11th to 20th	Day	9% 13% 42% 27% 8% 1	180
	21st to end	Day	14% 8% 29% 31% 14% 4	198
January	1st to 10th	Night	12% 12% 35% 30% 10% 1	950
	11th to 20th	Night	12% 10% 35% 32% 10% 1	950
	21st to end	Night	11% 10% 35% 31% 11% 1	931
February	1st to 10th	Night	14% 9% 29% 32% 13% 3	760
	11th to 20th	Night	11% 10% 31% 37% 10% 1	744
	21st to end	Night	8% 6% 31% 36% 16% 3	628
March	1st to 10th	Night	8% 7% 35% 37% 11% 2	760
	11th to 20th	Night	11% 11% 33% 32% 12% 1	760
	21st to end	Night	12% 11% 28% 34% 14% 1	836
April	1st to 10th	Night	15% 9% 34% 30% 11% 1	603
	11th to 20th	Night	16% 5% 33% 34% 12%	563
	21st to end	Night	15% 10% 24% 40% 11%	570
May	1st to 10th	Night	15% 7% 22% 36% 19% 2	570
	11th to 20th	Night	11% 6% 25% 36% 20% 1	499
	21st to end	Night	19% 7% 23% 31% 18% 2	411
June	1st to 10th	Night	17% 8% 26% 34% 13% 2	380
	11th to 20th	Night	15% 7% 30% 36% 11% 1	380
	21st to end	Night	7% 6% 26% 42% 18% 2	380
July	1st to 10th	Night	8% 3 20% 49% 21%	370
	11th to 20th	Night	7% 4 26% 45% 18% 1	368
	21st to end	Night	4 4 23% 45% 23% 2	416
August	1st to 10th	Night	8% 3 22% 41% 25% 1	529
	11th to 20th	Night	7% 2 21% 42% 27% 1	564
	21st to end	Night	10% 4 24% 38% 24% 1	627
September	1st to 10th	Night	11% 4 25% 43% 15% 1	570
	11th to 20th	Night	15% 5% 22% 41% 17%	703
	21st to end	Night	10% 6% 30% 38% 14% 2	760
October	1st to 10th	Night	15% 8% 27% 34% 17% 1	760
	11th to 20th	Night	14% 8% 31% 33% 12% 2	760
	21st to end	Night	13% 10% 36% 32% 9%	860
November	1st to 10th	Night	16% 11% 35% 30% 8% 1	936
	11th to 20th	Night	13% 13% 39% 28% 6% 1	950
	21st to end	Night	11% 10% 39% 32% 8% 1	950
December	1st to 10th	Night	12% 7% 35% 32% 11% 2	950
	11th to 20th	Night	10% 10% 39% 29% 11% 1	950
	21st to end	Night	13% 9% 35% 33% 8% 2	1045

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